Image decoding method, image coding method, image decoding apparatus, image coding apparatus, and image coding and decoding apparatus

ABSTRACT

The image decoding method includes: determining a context for use in a current block to be processed, from among a plurality of contexts; and performing arithmetic decoding on a bit sequence corresponding to the current block, using the determined context, wherein in the determining: the context is determined under a condition that control parameters of neighboring blocks of the current block are used, when the signal type is a first type, the neighboring blocks being a left block and an upper block of the current block; and the context is determined under a condition that the control parameter of the upper block is not used, when the signal type is a second type, and the second type is one of “cbf_luma”, “cbf_cb”, and “cbf_cr”.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional PatentApplication No. 61/502969 filed on Jun. 30, 2011. The entire disclosuresof the above-identified applications, including the specifications,drawings and claims are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to an image decoding method, an imagecoding method, an image decoding apparatus, an image coding apparatus,and an image coding and decoding apparatus, and in particular to animage decoding method, an image coding method, an image decodingapparatus, an image coding apparatus, and an image coding and decodingapparatus which use arithmetic coding or arithmetic decoding.

BACKGROUND ART

Natural image signals have statistical variations showing nonstationarybehavior. One of the entropy coding methods using the nonstationarystatistical variations is Context-Based Adaptive Binary ArithmeticCoding (CABAC) (see NPL 1). CABAC is employed as the ITU-T/ISOIECstandard for video coding, H.264/AVC.

The meaning of the terms used in the CABAC scheme will be describedhereinafter.

(1) “Context-Based Adaptive” means adapting the coding and decodingmethods to the statistical variations. In other words, “Context-BasedAdaptive” means predicting an appropriate probability as an occurrenceprobability of a symbol along with an event of surrounding conditions,when the symbol is coded or decoded. In coding, when an occurrenceprobability p(x) of each value of a symbol S is determined, aconditional occurrence probability is applied using an actual event or asequence of events F(z) as a condition.

(2) “Binary” means representation of a symbol using a binary sequence. Asymbol represented by a multi-value is once mapped to a binary sequencereferred to as “bin string”. A predicted probability (conditionalprobability) is switched and used for each of the sequence elements, andoccurrence of one of the events of the two values is represented by abit sequence. Accordingly, the probability of a value can be managed(initialized and updated) using a unit (binary element unit) smallerthan a unit of a signal type (see FIG. 2 and others of NPL 1).

(3) “Arithmetic” means that the bit sequence is generated not withreference to the correspondences in a table but by the computation. Inthe coding scheme using the tables of variable-length codes such asH.263, MPEG-4, and H.264, even each value of a symbol with an occurrenceprobability greater than 0.5 (50%) needs to be associated with onebinary sequence (bit sequence). Thus, a value with the greatestprobability needs to be associated with one bit for one symbol atminimum. In contrast, the arithmetic coding can represent the occurrenceof an event with a higher probability by an integer equal to or smallerthan one bit. When (i) there is a signal type in which the occurrenceprobability of having the first binary value as 0 exceeds 0.9 (90%) and(ii) an event having the first binary value as 0 successively occurs Ntimes, there is no need to output data of 1 bit N times for each valueof “0”.

CITATION LIST Non Patent Literature

-   [NPL 1] Detlev Marpe, et. al., “Context-Based Adaptive Binary    Arithmetic Coding in the H.264/AVC Video Compression Standard”, IEEE    Transaction on circuits and systems for video technology, Vol. 13,    No. 7, July 2003.-   [NPL 2] Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T    SG16 WP3 and ISO/IEC JTC1/SC29/WG11, 5th Meeting: Geneva, CH, 16-23    Mar., 2011, JCTVC-E603, ver.7 “WD3: Working Draft 3 of    High-Efficiency Video Coding”,    http://phenix.int-evry.fr/jct/doc_end_user/documents/5_Geneva/wg11/JCTVC-E603-v7.zip-   [NPL 3] Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T    SG16 WP3 and ISO/IEC JTC1/SC29/WG11, 4th Meeting: Daegu, KR, 20-28    Jan., 2011, “Common test conditions and software reference    configurations”, JCTVC-E700-   [NPL 4] Gisle Bjøntegaard, “Improvements of the BD-PSNR model,”    ITU-T SG16 Q.6 Document, VCEG-AI11, Berlin, July 2008

SUMMARY OF INVENTION Technical Problem

In such an image coding method and an image decoding method, memoryusage (memory capacity to be used) is desired to be reduced.

Here, the present invention has an object of providing an image codingmethod or an image decoding method that can reduce the memory usage.

Solution to Problem

In order to achieve the object, the image decoding method according toan aspect of the present invention is an image decoding method usingarithmetic decoding, and the method includes: determining a context foruse in a current block to be processed, from among a plurality ofcontexts; performing arithmetic decoding on a bit sequence correspondingto the current block, using the determined context to reconstruct abinary sequence, the bit sequence being obtained by performingarithmetic coding on a control parameter of the current block; andinversely binarizing the binary sequence to reconstruct the controlparameter of the current block, wherein the determining of a contextincludes: determining a signal type of the control parameter of thecurrent block; determining the context under a first condition thatdecoded control parameters of neighboring blocks of the current blockare used, when the signal type is a first type, the neighboring blocksbeing a left block and an upper block of the current block; anddetermining the context under a second condition that the decodedcontrol parameter of the upper block is not used, when the signal typeis a second type different from the first type, the first type is one of“split_coding_unit_flag” and “skip_flag”, and the second type is one of“cbf_luma”, “cbf_cb”, and “cbf_cr”.

Advantageous Effects of Invention

The present invention can provide an image coding method or an imagedecoding method that can reduce the memory usage.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the present invention. In the Drawings:

FIG. 1 is a functional block diagram of an image coding apparatusaccording to Embodiment 1;

FIG. 2 is a functional block diagram of a variable length coding unitaccording to Embodiment 1;

FIG. 3 is a table of a context model of a control parameter according toEmbodiment 1;

FIG. 4 is a flowchart indicating an arithmetic coding method accordingto Embodiment 1;

FIG. 5 is a functional block diagram of an image decoding apparatusaccording to Embodiment 2;

FIG. 6 is a functional block diagram of a variable length decoding unitaccording to Embodiment 2;

FIG. 7 is a flowchart indicating an arithmetic decoding method accordingto Embodiment 2;

FIG. 8 is a flowchart indicating a modification of the arithmeticdecoding method according to Embodiment 2;

FIG. 9 illustrates partitioned blocks (a tree structure) in accordancewith HEVC according to Embodiment 2;

FIG. 10 illustrates a multi-layer block structure according toEmbodiment 2;

FIG. 11 illustrates an arithmetic decoding method forsplit_coding_unit_flag according to Embodiment 3;

FIG. 12A is a table indicating a result of verification onsplit_coding_unit_flag according to Embodiment 3;

FIG. 12B is a table indicating a result of verification onsplit_coding_unit_flag according to Embodiment 3;

FIG. 13 illustrates an arithmetic decoding method for skip_flagaccording to Embodiment 3;

FIG. 14A is a table indicating a result of verification on skip_flagaccording to Embodiment 3;

FIG. 14B is a table indicating a result of verification on skip_flagaccording to Embodiment 3;

FIG. 15 is a table indicating an arithmetic decoding method forcbf_luma(cr,cb) according to Embodiment 3;

FIG. 16A is a table indicating a result of verification oncbf_luma(cr,cb) according to Embodiment 3;

FIG. 16B is a table indicating a result of verification oncbf_luma(cr,cb) according to Embodiment 3;

FIG. 17 illustrates context models using values of control parameterscorresponding to two neighboring blocks according to Embodiments;

FIG. 18 illustrates increase in memory usage when an upper block is usedaccording to Embodiments;

FIG. 19 illustrates an overall configuration of a content providingsystem for implementing content distribution services;

FIG. 20 illustrates an overall configuration of a digital broadcastingsystem;

FIG. 21 is a block diagram illustrating an example of a configuration ofa television;

FIG. 22 is a block diagram illustrating an example of a configuration ofan information reproducing/recording unit that reads and writesinformation from or on a recording medium that is an optical disc;

FIG. 23 illustrates an example of a configuration of a recording mediumthat is an optical disc;

FIG. 24A illustrates an example of a cellular phone;

FIG. 24B illustrates a block diagram showing an example of aconfiguration of the cellular phone;

FIG. 25 illustrates a structure of multiplexed data;

FIG. 26 schematically illustrates how each stream is multiplexed inmultiplexed data;

FIG. 27 illustrates how a video stream is stored in a stream of PESpackets in more detail;

FIG. 28 illustrates a structure of TS packets and source packets in themultiplexed data;

FIG. 29 illustrates a data structure of a PMT;

FIG. 30 illustrates an internal structure of multiplexed datainformation;

FIG. 31 illustrates an internal structure of stream attributeinformation;

FIG. 32 illustrates steps for identifying video data;

FIG. 33 is a block diagram illustrating an example of a configuration ofan integrated circuit for implementing the moving image coding methodand the moving image decoding method according to each of Embodiments;

FIG. 34 illustrates a configuration for switching between drivingfrequencies;

FIG. 35 illustrates steps for identifying video data and switchingbetween driving frequencies;

FIG. 36 illustrates an example of a look-up table in which the standardsof video data are associated with the driving frequencies;

FIG. 37A illustrates an example of a configuration for sharing a moduleof a signal processing unit; and

FIG. 37B illustrates another example of a configuration for sharing amodule of a signal processing unit.

DESCRIPTION OF EMBODIMENTS Embodiment 1 (Knowledge on Which the PresentInvention is Based)

The present inventors have found the following problems.

In High-Efficiency Video Coding (HEVC) that is a next-generation videocoding scheme, the context model in coding and decoding various controlparameters is being studied (NPL 2). The control parameter is includedin a coded bitstream, and is a parameter (flag, etc.) used in coding ordecoding processing. More specifically, the control parameter is asyntax element.

The context model is information indicating (i) which condition isconsidered for (ii) a signal of which unit (each element of amulti-value, a binary value, a binary sequence (bin string). Here,“which condition” indicates which condition with the number ofconditional elements is applied or which signal type of a controlparameter to be considered as a condition is appropriate. As theconditions are divided into smaller categories, that is, as the numberof conditions t increases, the number of the cases that hold true forthe conditions decreases. As a result, since the number of trainingsdecreases, the precision of the predicted probability decreases (forexample, see “dilution effect” in NPL 1).

Furthermore, decrease in the number of conditions indicates notconsidering a context (surrounding conditions), and being not adaptiveto the statistical variations.

In designing a context model, after determining a guideline fordesigning the model, it is necessary to consider the validity of themodel by conducting verifications specialized for an image, such as theverifications of statistical variations in details of an image and incontrol parameter for controlling coding and decoding of an image.

In H.264, using advanced events of a limited number for coding a symbolis a criterion of a rule, and the context models are classified intofour basic design types.

The first and second types relate to coding and decoding of a controlparameter.

The first context model uses coded values of up to two neighboring codedvalues (see NPL 1). Although the definition of the two neighboring codedvalues depends on each signal type, normally, values of correspondingcontrol parameters included in neighboring blocks to the left and upperof the current block are used.

The second type of context models is a type for determining a contextbased on a binary tree as an occurrence probability. More specifically,the second type of context models is applied to the control parametersmb_type and sub_mb_type.

The third and fourth types of context models relate to coding anddecoding of residual values (residual data), such as image data. Thethird type uses only the past coded or decoded values in the scanningorder of frequency coefficients (or quantized coefficients). The fourthtype determines a context according to the decoded and accumulatedvalues (levels).

The advantages of the design principle and implementation of theprobability transition model in H.264, such as the first type, have longbeen studied, and will be applied to HEVC that is being studied (see NPL2). For example, the first type (context model using neighboring syntaxelements) is being studied to be used for the control parametersalf_cu_flag, split_coding_unit_flag, skip_flag, merge_flag,intra_chroma_pred_mode, inter_pred_flag, ref_idx_lc, ref_idx_l0,ref_idx_l1, mvd_l0, mvd_l1, mvd_lc, no_residual_data flag, cbf_luma,cbf_cb, and cbf_cr (see 9.3.3.1.1 of NPL 2).

However, the present inventors have found that there is a problem in thememory usage in coding using the “context model using the twoneighboring blocks” of the first type.

FIG. 17 illustrates context models using values of control parameterscorresponding to the two neighboring blocks. Furthermore, FIG. 17illustrates the context models using the neighboring blocks in H. 264.

The block C in FIG. 17 includes a value of a control parameter SEcurrently to be coded and decoded. When the value of the controlparameter SE is coded, values of control parameters SE of the same typeincluded in the upper block A and the left block B that are alreadycoded are used. More specifically, the probability p(x) indicatingwhether the value x of the control parameter SE of the block C (or thefirst binary value of bin string of the control parameter SE) is 1 or 0is predicted based on a conditional probability p(x|(condition A (valueof the upper block) and condition B (value of the left block)) using, asconditions, the value of the control parameter SE of the upper block Aand the value of the control parameter SE of the left block B.

FIG. 18 illustrates increase in memory usage when an upper block isused.

In FIG. 18, (xP, yP) is a position of an upper left pixel of aprediction unit (PU, unit of motion prediction) including the block C.Here, the block C is a block including a control parameter (for example,skip_flag) currently to be coded. Furthermore, (xP, yA) in FIG. 18 is aposition of a pixel that is included in the block B and is used as acondition A (value of the control parameter skip_flag of the upperblock). Furthermore, (xL, yP) in FIG. 18 is a position of a pixel thatis included in the block A and is used as a condition B (value of thecontrol parameter skip_flag of the left block).

In order to code or decode the value of the control parameter skip_flagof the block C, the coding apparatus or the decoding apparatus needs tohold the value of skip_flag of PU (or a result of determination of acondition) corresponding to the position (xP, yA) included in the upperblock B and the position (xL, yP) included in the left block A. Assumingthat the picture has a horizontal width of 4096 pixels, in order to codeone control parameter skip_flag, it is necessary to hold all thedetermination values included in the upper row (Line L in FIG. 18). Inother words, one control parameter needs the memory capacity obtained by4096 pixels/block size. Here, the block C to be coded has variablesizes, for example, 64×64, 16×16, or 4×4. Furthermore, the block size ofthe block C to be later coded or decoded cannot be predicted when theblocks in the upper row (Line L) including (xP, yA) are coded ordecoded. This is because the size of each of the blocks in the lower row(row including the block C) is not known when the upper row (rowincluding the block A) is coded or decoded. Thus, the coding apparatusor the decoding apparatus needs to hold a value of a control parameter(or determination value) for each minimum block size, assuming that thesmallest block size from among all the sizes applied to the controlparameters is used as the block size of the lower row. The positions ofthe black circles in FIG. 18 indicate conditions that have to be held,although the conditional values are not actually necessary when thelower row (row including the block C) is coded and decoded.

Furthermore, the two neighboring blocks in FIG. 18 (the left block A andthe upper block B) follow the concept of the neighboring blocks inH.264, and no new perspective on the division of hierarchical blocks isintroduced. As described below, there are cases where such conditionalvalues to be referred to in FIG. 18 do not always make sense for controlparameters adapted to the recursive quad tree partitioning to beintroduced in HEVC, because the control parameters follow the recursiveexecution order, the hierarchical depth, or positions of blocks.

As such, the present inventors have found that the memory usageincreases by using the conditional values of the upper blocks inperforming arithmetic coding or decoding on the control parameters.Furthermore, the present inventors have found that the memory usagefurther increases in HEVC.

In contrast, the image decoding method according to an aspect of thepresent invention is an image decoding method using arithmetic decoding,and the method includes: determining a context for use in a currentblock to be processed, from among a plurality of contexts; performingarithmetic decoding on a bit sequence corresponding to the currentblock, using the determined context to reconstruct a binary sequence,the bit sequence being obtained by performing arithmetic coding on acontrol parameter of the current block; and inversely binarizing thebinary sequence to reconstruct the control parameter of the currentblock, wherein the determining of a context includes: determining asignal type of the control parameter of the current block; determiningthe context under a first condition that decoded control parameters ofneighboring blocks of the current block are used, when the signal typeis a first type, the neighboring blocks being a left block and an upperblock of the current block; and determining the context under a secondcondition that the decoded control parameter of the upper block is notused, when the signal type is a second type different from the firsttype, the first type is one of “split_coding_unit_flag” and “skip_flag”,and the second type is one of “cbf_luma”, “cbf_cb”, and “cbf_cr”.

With the structure, the image decoding method can reduce the memoryusage. More specifically, in the image decoding method, since thecontrol parameter of the upper block is not used for a control parameterof the second type, there is no need to hold the control parameter ofthe second type of the upper block. With the structure, compared to thecase where the left block and the upper block are used as uniformly“using a context model based on values of control parameters ofneighboring blocks”, the memory usage can be reduced according to theimage decoding method. Furthermore, the image decoding method canappropriately reduce the memory usage of the control parameter of thesecond type without, for example, failing to evaluate a BD-rate of animage.

Furthermore, according to the image decoding method, the contextappropriate for a hierarchical tree structure that is a data structurethat is not consider in the conventional H.264 and is unique to the newstandard HEVC can be used. Alternatively, memory reference can beperformed.

Furthermore, the second condition may be a condition that the decodedcontrol parameters of the left block and the upper block are not used.

With the structure, the image decoding method can reduce the memoryusage by not using the control parameter of the left block in additionto the control parameter of the upper block.

Furthermore, in the determining of a context, a predetermined contextmay be determined under the second condition, as the context for use inthe arithmetic decoding of the current block, when the signal type isthe second type.

With the structure, the image decoding method can reduce the processingamount.

Furthermore, the context may be determined under the second conditionaccording to a hierarchical depth of a data unit to which the controlparameter of the current block belongs, when the signal type is thesecond type.

With the structure, the image decoding method can select an appropriatecontext while reducing the memory usage.

Furthermore, the determining of a context may further include:determining whether or not the decoded control parameter of the upperblock is available in decoding, based on a position of the currentblock; and determining the context under the second condition, when thedecoded control parameter of the upper block is not available.

With the structure, the image decoding method can reduce the processingamount.

Furthermore, in the determining of a context, it may be determined thatthe decoded control parameter of the upper block is not available indecoding, when the current block is at a slice boundary.

Furthermore, in the determining of a context, it may be determinedwhether or not the decoded control parameter of the upper block isavailable in decoding, according to a hierarchical depth of a data unitto which the control parameter of the current block belongs.

Furthermore, the second type may be a control parameter having apredetermined data structure.

Furthermore, the determining of a context may further includedetermining a context of a control parameter of a second unit smallerthan a first unit by switching between the first condition and thesecond condition, based on a control parameter of the first unit.

Furthermore, the determining of a context may further includedetermining a context using a different condition for each case wherethe signal type is the “cbf_luma”, or the signal type is one of the“cbf_cb” and the “cbf_cr”.

Furthermore, the “split_coding_unit_flag” may indicate whether or notthe current block is partitioned into a plurality of blocks, the“skip_flag” may indicate whether or not the current block is to beskipped, the “cbf_luma” may indicate whether or not a luma transformblock of the current block contains one or more transform coefficientlevels not equal to 0, the “cbf_cb” may indicate whether or not a Cbtransform block of the current block contains one or more transformcoefficient levels not equal to 0, and the “cbf_cr” may indicate whetheror not a Cr transform block of the current block contains one or moretransform coefficient levels not equal to 0.

Furthermore, decoding processes in accordance with a first standard anddecoding processes in accordance with a second standard may be switchedaccording to an identifier indicating one of the first standard and thesecond standard, the identifier being included in a coded signal, andthe determining of a context, the performing, and the inverselybinarizing may be performed as the decoding processes in accordance withthe first standard, when the identifier indicates the first standard.

Furthermore, the image coding method according to an aspect of thepresent invention is an image coding method using arithmetic coding, andthe method includes: binarizing a control parameter of a current blockto be processed to generate a binary sequence; determining a context foruse in the current block, from among a plurality of contexts; andperforming arithmetic coding on the binary sequence using the determinedcontext to generate a bit sequence, wherein the determining of a contextincludes: determining a signal type of the control parameter of thecurrent block; determining the context under a first condition thatcontrol parameters of neighboring blocks of the current block are used,when the signal type is a first type, the neighboring blocks being aleft block and an upper block of the current block; and determining thecontext under a second condition that the control parameter of the upperblock is not used, when the signal type is a second type different fromthe first type, the first type is one of “split_coding_unit_flag” and“skip_flag”, and the second type is one of “cbf_luma”, “cbf_cb”, and“cbf_cr”.

With the structure, the image coding method can reduce the memory usage.More specifically, in the image coding method, since the controlparameter of the upper block is not used for a control parameter of thesecond type, there is no need to hold the control parameter of thesecond type of the upper block. With the structure, compared to the casewhere the left block and the upper block are used as uniformly “using acontext model based on values of control parameters of neighboringblocks”, the memory usage can be reduced according to the image codingmethod. Furthermore, the image coding method can appropriately reducethe memory usage of the control parameter of the second type without,for example, failing to evaluate a BD-rate of an image.

Furthermore, according to the image coding method, the contextappropriate for a hierarchical tree structure that is a data structurethat is not consider in the conventional H.264 and is unique to the newstandard HEVC can be used. Alternatively, memory reference can beperformed.

Furthermore, the image decoding apparatus according to an aspect of thepresent invention is an image decoding apparatus using arithmeticdecoding, and the apparatus includes: a context control unit configuredto determine a context for use in a current block to be processed, fromamong a plurality of contexts; an arithmetic decoding unit configured toperform arithmetic decoding on a bit sequence corresponding to thecurrent block, using the determined context to reconstruct a binarysequence, the bit sequence being obtained by performing arithmeticcoding on a control parameter of the current block; and an inversebinarization unit configured to inversely binarize the binary sequenceto reconstruct the control parameter of the current block, wherein thecontext control unit is configured to: determine a signal type of thecontrol parameter of the current block; determine the context under afirst condition that decoded control parameters of neighboring blocks ofthe current block are used, when the signal type is a first type, theneighboring blocks being a left block and an upper block of the currentblock; and determine the context under a second condition that thedecoded control parameter of the upper block is not used, when thesignal type is a second type different from the first type, the firsttype is one of “split_coding_unit_flag” and “skip_flag”, and the secondtype is one of “cbf_luma”, “cbf_cb”, and “cbf_cr”.

With the configuration, the image decoding apparatus can reduce thememory usage.

Furthermore, the image coding apparatus according to an aspect of thepresent invention is an image coding apparatus using arithmetic coding,and the apparatus includes: a binarization unit configured to binarize acontrol parameter of a current block to be processed to generate abinary sequence; a context control unit configured to determine acontext for use in the current block, from among a plurality ofcontexts; and an arithmetic coding unit configured to perform arithmeticcoding on the binary sequence using the determined context to generate abit sequence, wherein the context control unit is configured to:determine a signal type of the control parameter of the current block;determine the context under a first condition that control parameters ofneighboring blocks of the current block are used, when the signal typeis a first type, the neighboring blocks being a left block and an upperblock of the current block; and determine the context under a secondcondition that the control parameter of the upper block is not used,when the signal type is a second type different from the first type, thefirst type is one of “split_coding_unit_flag” and “skip_flag”, and thesecond type is one of “cbf_luma”, “cbf_cb”, and “cbf_cr”.

With the configuration, the image coding apparatus can reduce the memoryusage.

Furthermore, the image coding and decoding apparatus according to anaspect of the present invention is an image coding and decodingapparatus including the image decoding apparatus and the image codingapparatus.

The general or specific aspects may be implemented by a system, amethod, an integrated circuit, a computer program, or a recordingmedium, or by an arbitrary combination of the system, the method, theintegrated circuit, the computer program, and the recording medium.

The image decoding apparatus and the image coding apparatus according toan aspect of the present invention will be specifically described withreference to drawings.

Embodiments described hereinafter indicate specific examples of thepresent invention. The values, shapes, materials, constituent elements,positions and connections of the constituent elements, steps, and ordersof the steps indicated in Embodiments are examples, and do not limit thepresent invention. The constituent elements in Embodiments that are notdescribed in independent Claims that describe the most generic conceptof the present invention are described as arbitrary constituentelements.

Embodiment 1

An image coding apparatus according to Embodiment 1 of the presentinvention will be described. The image coding apparatus according toEmbodiment 1 determines a context by switching between (1) using theupper block and (2) without using the upper block, according to a signaltype of a control parameter in arithmetic coding. With the structure,the deterioration in image quality can be suppressed, and memory usagecan be reduced.

First, a configuration of the image coding apparatus according toEmbodiment 1 will be described.

FIG. 1 is a block diagram illustrating an image coding apparatus 100according to Embodiment 1.

The image coding apparatus 100 in FIG. 1 is an image coding apparatususing arithmetic coding, and codes an input image signal 121 to generatea bitstream 124. The image coding apparatus 100 includes a control unit101, a subtracting unit 102, a transformation and quantization unit 103,a variable length coding unit 104, an inverse-quantization andinverse-transformation unit 105, an adding unit 106, an intra predictionunit 107, an inter prediction unit 108, and a switch 109.

The control unit 101 calculates a control parameter 130 based on theinput image signal 121 to be coded. For example, the control parameter130 includes information on a picture type of the input image signal 121to be coded, a size of a unit of motion prediction (prediction unit, PU)of the current block to be coded, and control information of the unit ofmotion prediction. Here, the control parameter 130 (control data) itselfis to be coded. Thus, the control unit 101 outputs the control parameter130 to the variable length coding unit 104.

The subtracting unit 102 calculates a residual signal 122 that is adifference (residual value) between the input image signal 121 and animage prediction signal 129 on a block unit basis.

The transformation and quantization unit 103 transforms the residualsignal 122 into frequency coefficient values and quantizes the obtainedfrequency coefficient values into quantized transform coefficients 123(residual data).

The inverse-quantization and inverse-transformation unit 105 inverselyquantizes the quantized transform coefficients 123 into the frequencycoefficient values and inversely transforms the obtained frequencycoefficient values into a reconstructed residual signal 125.

The adding unit 106 adds the residual signal 125 to the image predictionsignal 129, and outputs a reconstructed image signal 126.

The intra prediction unit 107 performs intra prediction using thereconstructed image signal 126 to generate an image prediction signal127. The inter prediction unit 108 performs inter prediction using thereconstructed image signal 126 to generate an image prediction signal128

The switch 109 selects one of the image prediction signal 127 and theimage prediction signal 128, and outputs the selected signal as theimage prediction signal 129.

The variable length coding unit 104 codes, using the CABAC, thequantized transform coefficients 123 and the control parameter 130 foreach input block to generate the bitstream 124.

Next, the configuration of the variable length coding unit 104 will bedescribed.

FIG. 2 is a functional block diagram of the variable length coding unit104. The variable length coding unit 104 includes a binarizing unit 141,a context control unit 142, and a binary arithmetic coding unit 143. Thefollowing describes the variable length coding process on the controlparameter 130. Although the description about the variable length codingprocess on the quantized transform coefficients 123 is omitted, theprocess can be implemented, for example, using a known technique.

The binarization unit 141 binarizes the control parameter 130 togenerate a binary sequence 151. More specifically, the binarization unit141 is a processing unit that performs “II.1) binarization processing”according to NPL 1. The binarization unit 141 transforms the controlparameter 130 into the binary sequence 151 referred to as “bin string”for each signal type, according to a predetermined binarization method.The correspondence between the signal types and the binarization methodswill be described later. When the input control parameter 130 is onebinary value, such as a flag, the binarization unit 141 outputs thecontrol parameter 130 as the binary sequence 151 as it is.

The context control unit 142 determines a context for use in arithmeticcoding of the control parameter 130 included in a current block to beprocessed, from among a plurality of contexts (a probability statetable). Furthermore, the context control unit 142 outputs a contextindex 152 specifying the determined context to the binary arithmeticcoding unit 143.

More specifically, the context control unit 142 is a processing unitthat performs “2) context modeling” according to NPL 1. The contextcontrol unit 142 sequentially receives a plurality of elements includedin the binary sequence 151 output from the binary arithmetic coding unit143. The context control unit 142 selects one of the contexts to be usedfor the binary of the control parameter 130, according to the signaltype of the control parameter 130 and an element position of the binaryin the binary sequence 151, and outputs, to the binary arithmetic codingunit 143, the context index 152 that is an index indicating the selectedcontext.

Furthermore, the context control unit 142 holds the probability statetable of values (context index values) obtained by dividing the elementsin the binary sequence of the control parameter 130 into conditions ofconditional probabilities, as states of the context, and initializes andupdates the probability state table.

Furthermore, the context control unit 142 holds a state (probabilitystate index) for each occurrence condition τ (for each context), as afurther division of a signal type (for each element number in the binarysequence of the control parameter 130 when the number of elements in thebinary sequence is two or more; the same will apply hereafter). Thestate is represented by the total 7-bit value by combining theoccurrence probability P (internal ratio, typically, a 6-bit value) thatis the lower probability of one of two values 0 and 1, and a 1-bit valueindicating which one of the values has the higher probability.Furthermore, holding a state means initializing and updating the state.For example, the updating corresponds to changing the indexing thatindicates a current probability state (that is, a probability) as atransition among 64 finite states as in H.264.

When an event X at the most probable side having the highest probabilitybetween the two values occurs, a ratio of the probability at the mostprobable side is slightly increased. For example, the context controlunit 142 can slightly increase the ratio of the probability at the mostprobable side by incrementing or decrementing, by 1, the value of theprobability state index corresponding to 64 tables. On the other hand,when an event Not-X having the lower probability (against the predictedprobability) occurs, the context control unit 142 largely decreases theratio of the held most probable probability based on a predeterminedscale coefficient a (for example, ≈0.95) (see FIG. 6 of NPL 1). Thecontext control unit 142 according to Embodiment 1 transitions and holdsa state, based on a corresponding table index change value so as to beassociated with the change in consideration of α as in H.264.

The binary arithmetic coding unit 143 performs arithmetic coding on thebinary sequence 151 using the context determined by the context controlunit 142 to generate the bitstream 124 (bit sequence).

More specifically, the binary arithmetic coding unit 143 is a processingunit that performs “3) binary arithmetic coding” according to NPL 1. Thebinary arithmetic coding unit 143 performs arithmetic coding on thebinary sequence 151 using the context specified by the context index 152to generate the bitstream 124. Here, the arithmetic coding is to handleevents occurring for the control parameters 130 of various signal typesas a cumulative sum of probabilities, and determine correspondencesbetween the events by narrowing down the range to a predetermined rangeon one number line.

First, the binary arithmetic coding unit 143 divides the one number lineinto two half sections, according to the occurrence probabilities of twopossible values of the binary given from the context control unit 142.When the actual value occurring for the binary (for example, 0) is avalue with a higher probability (exceeding 0.5 (for example, 0.75)), thebinary arithmetic coding unit 143 maintains the lower limit “Low” in therange on the number line without change, and sets a value correspondingto a result of multiplying one time a scale coefficient 0.95 by theprobability 0.75 this time, to a new range. On the other hand, when theactually generated binary value is a predicted value with a lowerprobability, the binary arithmetic coding unit 143 shifts the lowerlimit “Low” by the higher probability, and changes the range accordingto the lower probability. The sections are held according to acumulative sum of results of multiplications of the probability ranges.When a value with a lower probability successively occurs, the precisionof the length of the range becomes soon lower than the precision thatcan be ensured by a computation. Here, the binary arithmetic coding unit143 enlarges (renorms) the range to maintain the precision, and outputsthe bit sequence indicating the current range. Conversely, when a valuewith a higher probability (0.95, etc.) successively occurs, theprobability values can bear a number of computations (state transitionsin the case of implementation by a table) until the length of the rangebecomes shorter than a predetermined length even with the multiplicationof the values. Thus, the number of symbols that can be cumulated untilthe bit is output is many.

FIG. 3 is a table in which the control parameters 130 each using acontext model based on a value of the control parameter 130 of aneighboring block are sorted out.

The meaning of each column will be described from the left of the table.

(c2) Signal type (syntax element) indicates a specific name of a signaltype of the control parameter 130. The meaning of each of the signaltypes will be described later.

(c3) Binarization scheme indicates a binarization scheme to be appliedto the control parameter 130 (SE) specified in the immediately leftcolumn. The binarization unit 141 performs the binarization process. Inthe column, “Fixed length” means that the binarization unit 141 outputsthe value of the control parameter 130 at the immediately left sectionas a binary sequence (bin string) of a fixed length. In HEVC, a signaltype of the control parameter 130 whose name ends with “flag” is onebinary value of either 0 or 1. Thus, the binarization unit 141 outputsonly the first element (binIdx=0) as the element of the binary sequence151, and does not output the elements after the second element(binIdx>=1). In other words, the binarization unit 141 outputs the valueof the control parameter 130 as the binary sequence 151 as it is.

Furthermore, “Variable length” in the column means that the binarizationunit 141 maps, to a binary sequence, the value of the control parameter130 using binary sequences with respective variable lengths whose valuesare associated to have binary lengths in ascending order of theoccurrence frequencies (bin string or binary sequences each with thenumber of elements 1), and outputs the binary sequence. For example, thebinarization unit 141 employs and outputs a scheme according to thesignal type, such as a (truncated) unary scheme, and a combination ofthe unary and other exponetional Golomb schemes (see “A. Binarization”of NPL 1). In the case of “Variable length”, the number of elements ofthe binary sequence 151 is sometimes limited to 1, or is equal to orlarger than 2. An inverse binarization unit in an image decodingapparatus to be described later performs transformation inverse to thebinarization scheme to reconstruct the input binary sequence into amulti-value or a flag value.

Regarding (c4) Context index of the first element (binIdx=0), thecontext control unit 142 indicates the choice of a context index(increment) to be applied to the first element included in a binarysequence generated according to the binarization scheme specified in thecolumn of c3. In the column, “0, 1, 2” indicates that the contextcontrol unit 142 selects and applies one of three probability statetables (contexts). For example, three context indexes with detailedconditions are prepared for the one signal type “skip_flag”, that is,three contexts are prepared, and the arithmetic coding is performed onthe context indexes.

Similarly, “0, 1, 2, 3” in the column c4 indicates that the context tobe applied to the first element (binIdx=0) included in the binarysequence 151 is selected from among one of four values, either 0, 1, 2,or 3. The binary sequence 151 is obtained by mapping, to a binarysequence, the value of the control parameter 130 of the signal typespecified in the column of c2, according to the binarization scheme inthe column of c3. The conditional expressions in the column will bedescribed later.

Regarding (c5) Left block condition L (condL), the context control unit142 indicates the left block condition to select one of 0, 1, and 2 atthe column c4. The left block condition L has a value of true or falsedetermined according to the value of the control parameter of the leftblock corresponding to the control parameter to be coded (or to bedecoded).

For example, in the case where the control parameter (SE) is skip_flag,the left block condition L has the value of true when skip_flag[xL][yL]indicates true (for example, 1), and has the value of false when itindicates false (for example, 0).

Regarding (c6) Upper block condition A, the context control unit 142indicates the upper block condition to select one of 0, 1, and 2 incoding or decoding elements of a sequence specified in the column c4.The upper block condition A has a value of true or false determinedaccording to the value of the control parameter of the upper blockcorresponding to the control parameter to be coded (or to be decoded).For example, in the case where the control parameter (SE) is skip_flag,the upper block condition A has the value of true when skip_flag[xA][yA]indicates true (for example, 1), and has the value of false when itindicates false (for example, 0).

Although not illustrated, the signal type of more than two bits isassociated with “(c7) Context increment to be applied to binIdx>=1”.This (c7) indicates the context model applied by the context controlunit 142 to a binary after the second element in the binary sequence(binary value of a binary sequence element including an index value ofbinIdx>=1).

In the coding method of Embodiment 1, the following operations areswitched according to the signal type of the control parameter 130 forthe left block condition L and the upper block condition A (operatedusing different patterns):

(Pattern 1) Using two neighboring blocks (a determination value of theleft block condition L and a determination value of the upper blockcondition A);

(Pattern 2) Using one neighboring block (only a determination value ofthe left block condition L); and

(Pattern 3) Using zero neighboring block (using neither a determinationvalue of the left block condition L nor a determination value of theupper block condition A).

FIG. 4 is a flowchart indicating an image coding method according toEmbodiment 1 that is performed by the variable length coding unit 104 inFIG. 2.

First, the binarization unit 141 maps the value of the control parameter130 to a binary sequence according to a scheme corresponding to thesignal type of the control parameter 130 (S101).

Next, the context control unit 142 obtains a basic value of a contextfor use in arithmetic coding of the control parameter 130 (S102). Forexample, the context control unit 142 determines the basic valueaccording to the picture type (I, P, or B).

Next, the context control unit 142 determines a context value using oneof the patterns 1 to 3, based on the signal type of the controlparameter 130 (S103). Here, determining a context value is equivalent todetermining an adjustment value (increment value CtxIdxInc) for thebasic value of the context.

First, the context control unit 142 determines the signal type of thecontrol parameter 130 (S103). When the signal type of the controlparameter 130 is the first type corresponding to the pattern 1 (thefirst type at S104), the context control unit 142 determines a contextvalue using a determination value derived from values of controlparameters of two neighboring blocks (block A and block B) (S105). Inother words, the context control unit 142 determines a context under acondition that the control parameters of the two neighboring blocks ofthe left block and the upper block are used. Here, the context controlunit 142 uses both of a result of the determination of (c5) condL and aresult of the determination of (c6) condA in FIG. 3. Accordingly, dataof one row of pictures are held for the control parameters of the firsttype.

On the other hand, when the signal type of the control parameter 130 isthe second type corresponding to the pattern 2 (the second type atS104), the context control unit 142 determines a context value using avalue of a control parameter of one neighboring block (one immediatelyneighboring block in coding order) (S106). In other words, the contextcontrol unit 142 determines the context value under a condition that thecontrol parameter of the upper block is not used.

On the other hand, when the signal type of the control parameter 130 isthe third type corresponding to the pattern 3 (the third type at S104),the context control unit 142 fixedly determines a context value withoutusing both of the control parameters of the upper block and the leftblock (S107).

Next, the context control unit 142 adds the increment determined at StepS103 to the basic value of the context index determined at Step S102 todetermine a context index value (S108).

Finally, the binary arithmetic coding unit 143 performs arithmeticcoding on the binary value of the first element using the context valuespecified by the context index value determined at Step S108 to generatethe bit sequence (bitstream 124) (S109).

Next, when the processes from Steps S102 to S109 are not executed on allthe elements included in the binary sequence (No at S110), the variablelength coding unit 104 performs the processes from Steps S102 to S109 onthe next element included in the binary sequence. On the other hand,when the processes from Steps S102 to S109 are completed on all theelements included in the binary sequence (Yes at S110), the variablelength coding unit 104 ends the coding processing on the controlparameter of the current block.

As described above, the image coding apparatus 100 according toEmbodiment 1 determines a context using the upper block in performingarithmetic coding on the control parameter of the first type, anddetermines a context without using the upper block for the controlparameters of the second and third types.

Compared to the case where the left block and the upper block are usedas uniformly “using a context model based on values of controlparameters of neighboring blocks”, the image coding apparatus 100 canreduce the memory usage with the configuration. Thus, the image codingapparatus 100 can suppress the deterioration in image quality, andreduce the memory usage.

Embodiment 2

Embodiment 2 will describe an image decoding apparatus that decodes thebitstream 124 generated by the image coding apparatus 100.

FIG. 5 is a block diagram illustrating an image decoding apparatus 200according to Embodiment 2. The image decoding apparatus 200 is an imagedecoding apparatus using arithmetic decoding, and decodes the bitstream124 to generate an image signal 229. Here, the bitstream 124 is, forexample, generated by the image coding apparatus 100.

The image decoding apparatus 200 includes a control unit 201, a variablelength decoding unit 202, an inverse quantization unit 204, an inversetransformation unit 205, an adding unit 206, an intra prediction unit207, and an inter prediction unit 208.

The image decoding apparatus 200 performs decoding processing for eachbitstream of a predetermined processing unit. The processing unit is,for example, a slice unit or a block unit.

The variable length decoding unit 202 performs arithmetic decoding onthe bitstream 124 to generate a control parameter 230 (control datasyntax element) and quantized transform coefficients 223 (residual datasyntax element values). The control unit 201 receives the generatedcontrol parameter 230.

The control unit 201 controls each of the processing units included inthe image decoding apparatus 200, according to the control parameter230.

The inverse quantization unit 204 inversely quantizes the quantizedtransform coefficients 223 into orthogonal transform coefficients 224.

The inverse transformation unit 205 inversely transforms the orthogonaltransform coefficients 224 to reconstruct a residual signal 225. Theadding unit 206 adds the residual signal 225 to an image predictionsignal (image signal 229) to generate a decoded image signal 226.

The intra prediction unit 207 performs intra prediction using thedecoded image signal 226 to generate an image prediction signal 227. Theinter prediction unit 208 performs inter prediction using the decodedimage signal 226 to generate an image prediction signal 228.

The switch 209 selects one of the image prediction signal 227 and theimage prediction signal 228, and outputs the selected signal as theimage signal 229 (image prediction signal).

Next, the configuration of the variable length decoding unit 202 will bedescribed.

FIG. 6 is a functional block diagram illustrating a configuration of thevariable length decoding unit 202. The variable length decoding unit 202includes a binary arithmetic decoding unit 243, a context control unit242, and an inverse binarization unit 241. The following describes thevariable length decoding process on the control parameter 230. Althoughthe description about the variable length decoding process on thequantized transform coefficients 223 is omitted, the process can beimplemented, for example, using a known technique.

The context control unit 242 determines a context for use in arithmeticdecoding of the control parameter 230 of the current block, from among aplurality of contexts. Furthermore, the context control unit 242 outputsa context index 252 specifying the determined context to the binaryarithmetic decoding unit 243.

More specifically, the context control unit 242 uses the same contextmodel as that of the context control unit 142 in FIG. 2 as a heldprobability transition model. When the arithmetic coding unit 143 uses64 probability states, the binary arithmetic decoding unit 243 alsoholds the 64 probability states. This is because both the coder and thedecoder need to interpret a range of the number line to be coded exactlyin the same manner. Thus, the decoder uses the same pattern as thepattern selected by the coder from among the three patterns 1 to 3.

The arithmetic decoding unit 243 performs arithmetic decoding on the bitsequence (bitstream 124) using the context determined by the contextcontrol unit 242 to reconstruct the binary sequence 251. Morespecifically, the arithmetic decoding unit 243 reconstructs the inputbit sequence into the binary sequence 251, according to the context(probability state table) specified by the context index given from thecontext control unit 242.

The inverse binarization unit 241 reconstructs the binary sequence 251into a control parameter 230 if necessary through the inversebinarization process. As such, the context control unit 142 included inthe image coding apparatus 100 and the context control unit 242 includedin the image decoding apparatus 200 use the same context model in bothof the arithmetic coding and the arithmetic decoding of a controlparameter of a certain signal type.

FIG. 7 is a flowchart indicating an image decoding method according toEmbodiment 2 that is performed by the variable length decoding unit 202.

First, the variable length decoding unit 202 obtains the bitstream 124(S201).

Next, the context control unit 242 determines a signal type of a controlparameter to be decoded, according to the data structure of thebitstream 124 (S202).

Next, the context control unit 242 determines a basic value of a contextfor use in arithmetic decoding of the control parameter to be decoded(S203). For example, the context control unit 242 determines the basicvalue according to the picture type (I, P, or B).

Next, the context control unit 242 determines a context value using oneof the patterns 1 to 3, based on the signal type of the controlparameter (S204). Here, determining a context value is equivalent todetermining an adjustment value (increment value CtxIdxInc) for thebasic value of the context. For example, the context control unit 242statically determines one of the patterns 1 to 3 based on the signaltype of the control parameter by following a predetermined table

The context control unit 242 switches between neighboring blocks for usein determining a context for obtaining a binary value of the firstelement included in the binary sequence 251 using the arithmeticdecoding, according to the signal type of the control parameter.

First, the context control unit 242 determines the signal type of thecontrol parameter 230 (S205). When the signal type is the first typecorresponding to the pattern 1 (the first type at S205), the contextcontrol unit 242 determines a context value using control parameters oftwo neighboring blocks (S206). In other words, the context control unit242 determines the context value under a condition that decoded controlparameters of the two neighboring blocks of the left block and the upperblock are used.

On the other hand, when the signal type is the second type correspondingto the pattern 2 (the second type at S205), the context control unit 242determines a context value using a value of a control parameter of oneneighboring block (one immediately neighboring block in coding order)(S207). In other words, the context control unit 242 determines thecontext value under a condition that the decoded control parameter ofthe upper block is not used.

On the other hand, when the signal type is the third type correspondingto the pattern 3 (the third type at S205), the context control unit 242fixedly determines a context value (S208). In other words, the contextcontrol unit 242 determines the context value under a condition that thedecoded control parameters of the upper block and the left block are notused.

Next, the context control unit 242 adds the increment determined at StepS204 to the basic value of the context index determined at Step S203 todetermine a context index value (S209).

Next, the binary arithmetic decoding unit 243 determines one of theelements of the binary sequence through decoding using the context valueindicated by the context index value given from the context control unit242 (S210).

Next, when the processes from Steps S203 to S210 are not executed on allthe elements included in the binary sequence (No at S211), the variablelength decoding unit 202 performs the processes from Steps S203 to S210on the next element included in the binary sequence.

On the other hand, when the processes from Steps S203 to S210 arecompleted on all the elements included in the binary sequence (Yes atS211), the inverse binarization unit 241 changes one or more of theelements of the binary sequence 251 obtained by repeating the processesfrom Steps S203 to S210 more than one time to generate the controlparameter 230 (S212).

As described above, the image decoding apparatus 200 according toEmbodiment 2 determines a context using the upper block in performingarithmetic decoding on the control parameter of the first type, anddetermines a context without using the upper block for the controlparameters of the second and third types.

Compared to the case where the left block and the upper block are usedas uniformly “using a context model based on values of controlparameters of neighboring blocks”, the image decoding apparatus 200 canreduce the memory usage with the configuration. Thus, the image decodingapparatus 200 can suppress the deterioration in image quality, andreduce the memory usage.

For example, when the binary sequence 251 is a flag and has only oneelement, that is, the binary sequence 251 is composed of 1 binary, theinverse binarization unit 241 may output the binary sequence 251 as itis.

In addition to the description above, the control unit 101 or 201 maycontrol each of the processing units or refer to a value of a memory,through a signal line that is not illustrated.

Although the context control unit 142 or 242 switches between the threepatterns 1 to 3 according to a signal type of a control parameter in theabove description, it may switch between two of the patterns 1 to 3according to the signal type. In other words, the context control unit142 or 242 may switch between using and not using the upper blockcondition, according to a signal type of a control parameter.

Furthermore, the context control unit 142 or 242 may change a method ofswitching between the context models selected in such a manner(including a case where the context model increment is changed; the samewill apply hereafter) according to predetermined image information. Forexample, the context control unit 142 or 242 may further switch theswitching policy itself, according to the amount of memory, or the sizeof the horizontal width or a sampling format of an image that affectsthe number of trainings of each context.

Although the context control unit 142 or 242 switches between using andnot using the upper block condition as the simplified description, thecontext control unit 142 or 242 may combine a case where the upper blockis not available to the switching and apply the combined case. Forexample, the context control unit 142 or 242 may change the switchingpolicy itself, according to whether or not a slice to be processed is anentropy slice (entropy_slice_flag indicates 1 or 0). Similarly, when theavailability of the upper neighboring block cannot be ensured, thecontext control unit 142 or 242 may change the switching policy so asnot to use the upper block.

For example, as illustrated in FIG. 8, the context control unit 142 or242 may switch the determination policy of the context model between thefirst determination criterion (S302) and the second determinationcriterion (S303), according to a value of a parameter of a predeterminedunit. Here, “according to a value of a parameter of a predeterminedunit” means according to whether or not a slice is an entropy slice asdescribed above. Furthermore, the first determination criterion is acriterion based on which the processes in FIG. 7 are performed. Thesecond determination criterion is a criterion excluding Step S204 inFIG. 7, and is, for example, a conventional criterion. This isequivalent to determining the context index increment, using a parameterof a predetermined local unit and a value of a parameter of a unitlarger than the predetermined local unit.

In other words, the context control unit 142 or 242 may switch from adetermination criterion to be applied to a unit smaller than the firstunit, to another determination criterion based on a value of a controlparameter of the first unit.

Furthermore, the context control unit 142 or 242 may change thedetermination criterion to be used, according to the characteristics ofan image system. For example, the context control unit 142 or 242 maychange the determination criterion to be used, according to intervals ofI-pictures (setting values of IntraPeriod).

Although the context control unit 142 or 242 switches between thedetermination criterions according to the above conditions, it mayswitch whether or not the upper block is used.

Furthermore, the context control unit 142 or 242 may determine whetheror not a control parameter of the upper block is used, according towhether or not the control parameter of the upper block is available incoding or decoding based on a position of the control parameter. Inother words, the context control unit 142 or 242 may determine whetheror not the control parameter of the upper block is available indecoding, based on a position of the current block, and determine acontext using one of the patterns 2 and 3 when the control parameter ofthe upper block is not available. Furthermore, the context control unit142 or 242 may determine whether or not a reference value of the upperblock is available based on a tree structure for partitioning TU, CU, orPU blocks. In other words, the context control unit 142 or 242 maydetermine whether or not the control parameter of the upper block isavailable in decoding, according to the hierarchical depth of a dataunit to which each of the control parameters to be processed belongs.

FIG. 9 illustrates a relationship between a picture, slices, and blocksin accordance with the HEVC standard. One picture is partitioned intoone or more slices. In the example of FIG. 9, the picture is partitionedinto two slices (SLICE 1 and SLICE 2). One of the slices includes blocks301 (for example, treeblocks). Here, the block 301 is the largest unitas a certain control unit when a slice is partitioned in a predeterminedsize, and has a size of a root when the unit is at the root in thehierarchically-partitioned structure.

In the example of FIG. 9, SLICE 2 starts from a block 301A, and iscomposed of one sequence including blocks to the bottom right corner ofthe picture through the hatched blocks 301B and 301C. One of the hatchedblocks in FIG. 9 is one block (TreeBlock) to be currently processed.

Each of the blocks 301 includes N×M pixels. One of the blocks 301 isrecursively partitioned inside (typically into four). In other words,one TreeBlock conceptually composes one quad tree. In the block 301B inFIG. 9, the upper right block obtained by partitioning the hatched block301B into four are recursively partitioned into four blocks twice. Inother words, the block 301B includes 10 logical units from theupper-left zero-th unit to the lower-right ninth unit that arepartitioned with a certain perspective.

Here, the perspective indicates the concept of a plurality of treeshaving different depths with a root as a base point, such as a treeregarding a coding unit (CU) and a tree regarding residual_data. Here, avalue of each control parameter belongs to one of leaf nodes.

Here, whether or not a value of a control parameter of a certain signaltype included in an upper block is actually available depends on a typeof a tree to which the control parameter belongs. Thus, the contextcontrol unit 142 or 242 may change a determination criterion accordingto a type of a tree to which the control parameter belongs. This changeis equivalent to the change to a syntax unit. For example, the contextcontrol unit 142 or 242 may use the pattern 2 or 3 in which the upperblock is not used for data of an adaptive filter with a data structuresuch as alf_param, whereas it may use the context model policy(pattern 1) for the other syntaxes as conventionally used. In otherwords, the second type or the third type may be a control parameterhaving a predetermined data structure. Furthermore, this means that thedetermination criterion may be changed according to the type of a treeof a neighboring block.

Furthermore, whether or not the value of the control parameter can beactually used or produces the advantage of reducing the memory usagediffers depending on a position of a block in the hierarchicalrelationship. In other words, the context control unit 142 or 242 mayswitch between using or not using the upper block, according to a depthof a block and a hierarchical position of the block.

For example, in FIG. 9, the numbers 0 to 9 in the block 301B are indecoding order. In this case, the control parameters of the blocks 1 and2 are available when the block 4 is coded or decoded.

Furthermore, in order to reduce memory usage, the context control unit142 or 242 may select the pattern 1 using the upper block, when theblock is not at a depth 0 and the own position is one of the second tothe subsequent elements in the vertical partitioning. Here, “depth”indicates the depth from the root. In other words, when a certain blockis defined as block[xn],[y0][depth], the determination criterion may bechanged according to whether or not the current block satisfiesblock[xn][(y0)+1][depth]. In other words, the upper blocks are used forthe blocks 4 to 9 in FIG. 9. When the tree is coded or decoded in theorder as numbered (starting from 0 and ending at 9), it is clear thatthe blocks 4 to 9 can use the control parameters included in the upperblocks. Furthermore, there is an advantage that these blocks have onlyto temporally hold data. Furthermore, this indicates that the contextvalue is determined according to the 3D position including the depth inaddition to the x and y coordinates. Besides, a conditional value of ablock in the higher layer can be used (followed) as a conditional valueof a block in the lower layer.

Furthermore, the context control unit 142 or 242 may change thesecriteria in consideration of the position relationship between thecurrent block and the other slices. Hereinafter, the three hatchedblocks 301A, 301B, and 301C in FIG. 9 will be described.

Here, the block 301A is a start block, and both of the left block andthe upper block of the block 301A are included in another slice. Theupper block of the block 301B is included in another slice. Both of theleft block and the upper block of the block 301C are included in thesame slice including the block 301C. The context control unit 142 or 242may switch the criterion according to such a condition. In other words,the context control unit 142 or 242 may switch the criterion (i)according to whether or not the upper block is included in anotherslice, (ii) according to whether or not the left block is included inanother slice, or (iii) according to both (i) and (ii). In other words,the context control unit 142 or 242 may determine that the controlparameter of the upper block is not available in decoding when thecurrent block is at the slice boundary. Accordingly, when the decodingprocessing on the upper SLICE 1 is not completed, for example, it ispossible to perform the decoding processing in consideration of whetheror not SLICE 2 can obtain information by itself.

Next, the hierarchical processing unit (multi-layer block structure)will be described. FIG. 10 illustrates the hierarchical processing unit(multi-layer block structure).

The image coding apparatus 100 codes moving pictures on a per processingunit, and the image coding apparatus 200 decodes a coded stream on a perprocessing unit. The processing unit is layered by partitioning theprocessing unit into small processing units and further partitioning thesmall processing units into smaller processing units. As the processingunit is smaller, the depth of the processing unit is greater and ishierarchically lower, and the value indicating the depth is larger.Conversely, as the processing unit is larger, the depth of theprocessing unit is less and is hierarchically higher, and the valueindicating the depth is smaller.

The processing unit includes a coding unit (CU), a prediction unit (PU),and a transformation unit (TU). A CU is a block of 128×128 pixels atmaximum, and is a unit corresponding to a conventional macroblock. A PUis a basic unit for the inter prediction. A TU is a basic unit fororthogonal transformation, and has a size identical to that of PU ormuch smaller than PU. A CU is, for example, partitioned into 4 sub-CUs,and one of the sub-CUs includes a PU and a TU having the same size asthat of the sub-CU (here, PU and TU overlap one another). For example,the PU is further partitioned into 4 sub-PUs, and the TU is furtherpartitioned into 4 sub-CUs. When the processing unit is partitioned intosmaller processing units, each of the smaller processing units isreferred to as a sub-processing unit. For example, when the processingunit is a CU, the sub-processing unit is a sub-CU. When the processingunit is a PU, the sub-processing unit is a sub-PU. Furthermore, when theprocessing unit is a TU, the sub-processing unit is a sub-TU.

More specifically, the below indicates the details.

One picture is partitioned into one or more slices. A slice is asequence of the largest coding unit. The position of the largest codingunit is indicated by an address of the largest coding unit IcuAddr.

Each of the coding units including the respective largest coding unitsis partitioned into four coding units. As a result, a quad tree havingthe size of a CU is constructed. The position of the CU is indicated bya coding unit index cuIdx having a sample (pixel or coefficients) at theupper left corner of the largest coding unit as a starting point.

When partitioning of a CU is not permitted, the CU is handled as a PU.Similarly as the CU, the position of a PU is indicated by a predictionunit index puIdx having a sample at the upper left corner of the largestcoding unit as a starting point.

The PU may include partitions (PU partitions or sub-PUs). The PUpartition is indicated by a prediction-unit partition index puPartIdxhaving a sample at the upper left corner of the PU as a starting point.

The PU may include TUs. Similarly as the CU, the TU may be partitionedinto four smaller TUs (sub-TUs). This indicates the permission of thequad tree partitioning of a residual signal. The position of the TU isindicated by a transformation unit index tuIdx having a sample at theupper left corner of the PU as a starting point.

Here, the definition of each of the processing units is as follows:

CTB (coding tree block): Basic unit for identifying quad treepartitioning of a square region. Having various square sizes;

LCTB (largest coding tree block): The largest CTB permitted in a slice.A slice includes a plurality of LCTBs that do not overlap one another;

SCTB (smallest coding tree block): The smallest CTB permitted in aslice. Partitioning of a SCTB into smaller CTBs is not emitted

PU (prediction unit): Basic unit for identifying prediction processing.A PU is as large as a CU in which partitioning is not permitted.Although partitioning a CU into four square regions is permitted, a PUcan be partitioned into a plurality of partitions having any shape;

TU (transform unit): Basic unit for identifying transformation andquantization;

CU (coding unit): Same as CTB;

LCU (largest coding unit): Same as the largest CTB; and

SCU (smallest coding unit): Same as the smallest CTB.

Furthermore, quantization parameters include at least one of a deltaquantization scale parameter (delta QP or QP delta), a quantizationoffset parameter, an index (Q matrix select idc), and a quantizationdead zone offset parameter. The index is for selecting one of quantizedscaling matrices.

The delta quantization scale parameter (delta QP or QP delta) is adifference between a quantization scale parameter to be applied totransform coefficients and a quantization scale parameter specified by asequence header or a slice header (or a quantization scale parameterimmediately before in Z scanning order).

The quantization offset parameter is also referred to as a quantizationoffset, and is an adjustment value (offset value) for rounding a signalin performing quantization. Thus, when the image coding apparatus 100performs quantization, it codes the quantization offset. Then, the imagedecoding apparatus 200 decodes the coded quantization offset. Next, theimage decoding apparatus 200 performs correction using the quantizationoffset when inversely quantizing the transform coefficients.

An index (Qmatrix select idc) is referred to as an adaptive quantizationmatrix, and indicates which quantization scaling matrix is used fromamong a plurality of quantization scaling matrices. Furthermore, whenthere is only one quantization scaling matrix, Qmatrix select idcindicates whether or not the quantization scaling matrix is used. Theadaptive quantization matrix can be controlled per block unit(processing unit).

The quantization dead zone offset parameter is referred to as anadaptive dead zone, and is control information for adaptively changing adead zone per block. The dead zone is a width whose frequencycoefficients become 0 by quantization (last width that becomes +1 or −1after the quantization).

Although a case where the pattern 3 with which a predetermined fixedvalue is used as a context value is described hereinbefore, the case maybe performed under the condition that the control parameters of theupper block and the left block are not used, and further under thecondition without using the control parameters of the upper block andthe left block as the pattern 3. For example, the context control unit142 or 242 may determine a context according to the hierarchical depthof a data unit to which each of the control parameters belongs, as thepattern 3.

Embodiment 3

Embodiment 3 will describe which signal type should be used as the firsttype and the second type (or the third type).

More specifically, the present inventors have verified each of thesignal types below among the signal types as indicated in FIG. 3(Section 9.3.3.1.1.1 of NPL 2). Each of the signal types has beenverified, because there are various parameters, and it is difficult topredict whether or not each pattern of the other signal types satisfiesthe validity, based on a result of the verification on one of the signaltypes (which one of the patterns 1 to 3 is appropriate).

The verification is in conformity with the structure (setting parameterand software version HM3.0) described in JCTVC-E700, “Common testconditions and software reference configurations” (see NPL 3).Furthermore, each of the test images has a length limited to 49 frames.

The image coding method and the image decoding method according toEmbodiment 3 relate to CABAC. Thus, the verification has been conductedusing the following four test patterns that are a set of setting valueseach indicating 1 as the value of Symbol Mode (#0:LCEC, 1:CABAC):

4.1 Intra, high-efficiency setting;

4.3 Random access, high-efficiency setting;

4.5 Low delay, high-efficiency setting; and

4.7 Low delay, high-efficiency setting (P slices only).

The evaluation is made based on an evaluation value called a “BD-rate”that is used as an evaluation standard uniformly used for animplementation evaluation in HEVC. Y BD-rate, U BD-rate, and V BD-rateare BD-rates for a YUV color space, and are evaluation standard values.According to VCEG-AI11 (NPL 4), the BD-rate is an evaluation valueobtained by integrating two pairs of code amounts with a result of PSNR,and representing the coding efficiency according to the area ratio.Furthermore, the BD-rate indicating a minus value means that the codingefficiency has been improved. The comparison criteria are based on aresult of the output of a reference program which implements thepattern 1. The results of the patterns 2 and 3 are shown with respect tothe result of the pattern 1.

The following describes a result of the verification on each of thesignal types:

(First verification) split_coding_unit_flag;

(Second verification) skip_flag; and

(Third verification) cbf luma, cbf_cr, cbf_cb.

(First verification) split_coding_unit_flag

FIG. 11 illustrates an arithmetic decoding method forsplit_coding_unit_flag.

The verification is conducted by changing the context model from thepattern 1 to the pattern 2 or 3 only for a signal type to be verified,without changing the context model for the other signal types and theverification parameter specified in NPL 3. In the column in FIG. 11, thevalue of “Fixed” indicates that the condition (the left block conditionor the upper block condition) of the column specified by “Fixed” is notused when a context value (or increment) is derived. In other words,when only one of the left block condition and the upper block conditionis “Fixed”, only the other condition is used. Furthermore, when both ofthe left block condition and the upper block condition are “Fixed”, apredetermined value (for example, 0) is used as a context value (orincrement).

The meaning of the signal type “split_coding_unit_flag” is defined asfollows.

split_coding_unit_flag[x0][y0] specifies whether a coding unit is splitinto coding units with half horizontal and vertical size. The arrayindices x0, y0 specify the location (x0, y0) of the top-left luma sampleof the considered coding block relative to the top-left luma sample ofthe picture. In other words, “split_coding_unit_flag” indicates whetheror not the target Cu is partitioned into four. More specifically, thetarget CU is partitioned when split_coding_unit_flag indicates 1,whereas the target Cu is not partitioned when split_coding_unit_flagindicates 0.

Data of split_coding_unit_flag is structured into a coding tree syntaxas a syntax. The image decoding apparatus parses a bit sequence inaccordance with the syntax of this data structure.

FIGS. 12A and 12B are tables for describing results of the verificationon split_coding_unit_flag.

FIG. 12A indicates the result of the verification using one neighboringblock (only a determination value of the left block condition L) of thepattern 2. FIG. 12B indicates the result of the verification using zeroneighboring block (using neither the upper block condition L nor theleft block condition L) of the pattern 3.

The result of the verification in each of FIGS. 12A and 12B indicatesthe increment and decrement of the BD-rate according to the four testpatterns.

Furthermore, the evaluation value is represented by the evaluationstandard indicating a value relative to an evaluation value in the caseof the pattern 1 in which both of the left block and the upper block areused. More specifically, when the evaluation value is positive, theresult is inferior to the evaluation value (BD-rate) in the case of thepattern 1. Furthermore, when the evaluation value is negative, theresult is more improved than the evaluation value in the case of thepattern 1.

The result clarifies that the pattern 1 is superior as a pattern of acontext model for split_coding_unit_flag. In other words, the evaluationvalues obtained by the patterns 2 and 3 are inferior to that of thepattern 1.

Thus, when the signal type of a control parameter issplit_coding_unit_flag, the context control unit 142 or 242 determines acontext value using the pattern 1 that is a conventional pattern of acontext model, in terms of the BD-rate.

(Second verification) skip_flag

FIG. 13 illustrates an arithmetic decoding method for skip_flag. Here,the verification method is the same as that in the first verification.

The meaning of the signal type “skip_flag” is defined as follows.

skip_flag[x0][y0] equal to 1 specifies that for the current coding unit,when decoding a P or B slice, no more syntax elements except the motionvector predictor indices are parsed after skip_flag[x0][y0].skip_flag[x0][y0] equal to 1 specifies that the coding unit is not to beskipped. The array indices x0, y0 specify the location (x0, y0) of thetop-left luma sample of the considered coding block relative to thetop-left luma sample of the picture. In other words, skip_flag indicateswhether or not the target CU is to be skipped (handled as a skippedblock).

Data of skip_flag is structured into a coding unit syntax as a syntax.In other words, skip_flag is set for each Cu. The image decodingapparatus parses a bit sequence in accordance with the syntax of thisdata structure.

FIGS. 14A and 14B are tables for describing results of the verificationon skip_flag.

FIG. 14A indicates the result of the verification using one neighboringblock (only a determination value of the left block condition L) of thepattern 2. FIG. 14B indicates the result of the verification using zeroneighboring block (using neither the upper block condition L nor theleft block condition L) of the pattern 3.

The result of the verification in each of FIGS. 14A and 14B indicatesthe increment and decrement of the BD-rate according to the four testpatterns as described for the first verification. Furthermore, themeaning of the evaluation value is the same as that of the firstverification.

The result clarifies that the pattern 1 is superior as a pattern of acontext model for “skip_flag”. In other words, the evaluation valuesobtained by the patterns 2 and 3 are inferior to that of the pattern 1.

Thus, when the signal type of a control parameter is “skip_flag”, thecontext control unit 142 or 242 determines a context value using thepattern 1 that is a conventional pattern of a context model, in terms ofthe BD-rate.

(Third verification) “cbf_luma, cbf_cr, cbf_cb”

FIG. 15 is a table indicating an arithmetic decoding method forcbf_luma, cbf_cr, and cbf_cb.

The meaning of the signal type “cbf_luma” is defined as follows.

cbf_luma[x0][yO][trafoDepth] equal to 1 specifies that the lumatransform block contains one or more transform coefficient levels notequal to 0. The array indices x0, y0 specify the location (x0, y0) ofthe top-left luma sample of the considered transform block relative tothe top-left luma sample of the picture. The array index trafoDepthspecifies the current subdivision level of a coding unit into blocks forthe purpose of transform coding. trafoDepth is equal to 0 for blocksthat correspond to coding units.

In other words, the position of the luma transform block is defined as avalue of a three-dimensional array including a hierarchical depth(trafoDepth) relative to a layer of a CU, in addition to the verticaland horizontal elements.

Furthermore, a signal type “cbf_cb” defines cbf_luma regarding luma forchroma (cb). The meaning of the signal type “cbf_cb” is defined asfollows.

cbf_cb[x0][y0][trafoDepth] equal to 1 specifies that the Cb transformblock contains one or more transform coefficient levels not equal to 0.The array indices x0, y0 specify the location (x0, y0) of the top-leftluma sample of the considered transform block relative to the top-leftluma sample of the picture. The array index trafoDepth specifies thecurrent subdivision level of a coding unit into blocks for the purposeof transform coding. trafoDepth is equal to 0 for blocks that correspondto coding units. When cbf_cb[x0][y0][trafoDepth] is not present andPredMode is not equal to MODE_INTRA, the value ofcbf_cb[x0][y0][trafoDepth] is inferred to be equal to 0.

In other words, the position of the Cb transform block is defined as avalue of a three-dimensional array including a hierarchical depth(trafoDepth) relative to a layer of a CU, in addition to the verticaland horizontal elements.

Furthermore, a signal type “cbf_cr” defines cbf_luma regarding luma forchroma (cr). The meaning of the signal type “cbf_cr” is defined asfollows.

cbf_cr[x0][y0][trafoDepth] equal to 1 specifies that the Cb transformblock contains one or more transform coefficient levels not equal to 0.The array indices x0, y0 specify the location (x0, y0) of the top-leftluma sample of the considered transform block relative to the top-leftluma sample of the picture. The array index trafoDepth specifies thecurrent subdivision level of a coding unit into blocks for the purposeof transform coding. trafoDepth is equal to 0 for blocks that correspondto coding units. When cbf_cr[x0][y0][trafoDepth] is not present andPredMode is not equal to MODE_INTRA, the value ofcbf_cr[x0][y0][trafoDepth] is inferred to be equal to 0.

In other words, the position of the Cb transform block is defined as avalue of a three-dimensional array including a hierarchical depth(trafoDepth) relative to a layer of a CU, in addition to the verticaland horizontal elements.

FIGS. 16A and 16B are tables for describing results of the verificationon cbf_luma, cbf_cr, and cbf_cb.

FIG. 16A indicates the result of the verification using one neighboringblock (only a determination value of the left block condition L) of thepattern 2. FIG. 16B indicates the result of the verification using zeroneighboring block (using neither the upper block condition L nor theleft block condition L) of the pattern 3.

The result of the verification in each of FIGS. 16A and 16B indicatesthe increment and decrement of the BD-rate according to the four testpatterns as described for the first verification. Furthermore, themeaning of the evaluation value is the same as that of the firstverification.

The result is different from those of the first verification ofsplit_coding_unit_flag and the second verification of skip_flag. Thereis no significant difference in BD-rate between the patterns 1 and 2 or3 as a pattern of a context model for cbf_luma, cbf_cr, and cbf_cb.

Thus, under a mixed environment with a plurality of control parametersof signal types, the context control unit 142 or 242 determines acontext value without using the upper block as a neighboring blockparticularly when the signal type of the control parameter is cbf_luma,cbf_cr, and cbf_cb. In other words, the context control unit 142 or 242determines a context value using the pattern 2 or 3 when the signal typeof the control parameter is cbf_luma, cbf_cr, and cbf_cb. In otherwords, the first type includes “split_coding_unit_flag” or “skip_flag”,and the second type or the third type includes “cbf_luma, cbf_cr, andcbf_cb”. Accordingly, the image coding apparatus and the image decodingapparatus according to Embodiment 3 can reduce memory usage whilesuppressing the decrease in the BD-rate.

When the pattern 2 is compared with the pattern 3 for cbf_luma, cbf_cr,and cbf_cb, these BD-rates have no significant difference. Thus, it ispreferred to use the pattern 3 for cbf_luma, cbf_cr, and cbf_cb.Accordingly, it is possible to further reduce the memory usage and theprocessing amount.

Furthermore, cbf_luma, cbf_cb, and cbf_cr are values of athree-dimensional array having a depth. Thus, as described for FIG. 9according to Embodiment 2, distances (remoteness) between neighboringreference values in the decoding order (including recursive executionorder and will be the same hereinafter) are different according to therespective hierarchical depths. Accordingly, whether or not the value ofthe control parameter is actually available or produces the advantagefor reducing the memory usage differs depending on a position of a blockin the hierarchical relationship.

Thus, the context control unit 142 and 242 may change a determinationcriterion of a conditional value according to the hierarchical depth.For example, the context control unit 142 and 242 may use (follow) aconditional value of a block in the higher layer as a conditional valueof a block in the lower layer.

Furthermore, the context control unit 142 and 242 may change thesecriteria in consideration of the position relationship with anotherslice, in addition to the above or singly.

As a result of the above verifications, the following detailedmodification is conceivable. Whether or not the dilution effect occursdepends on the number of trainings to which the condition is applied.Generally, Y that represents luminance in Y, U, and V, such as the 4:2:0format, is greater in number of samples than the other two axes (U andV). Thus, one boundary that should be distinguished is between (a) lumaand (b) a pair of cb and cr.

For example, the pattern 3 may be applied to (a) cbf_luma, and the otherpattern 2 or 1 may be applied to (b) cbf_cb and cbf_cr. In other words,the context control unit 142 and 242 may determine a context using adifferent condition for each case where the signal type is the“cbf_luma”, or the signal type is one of the “cbf_cb” and the “cbf_cr”.

Here, when the number of trainings is sufficient, it is preferred thatthe context control unit 142 and 242 increase the number of (context)conditions for the precision. Furthermore, it is preferred that thecontext control unit 142 and 242 decrease the number of the contextconditions when the number of trainings is less. Thus, the contextcontrol unit 142 and 242 may switch between these conditions accordingto the resolution. Furthermore, the context control unit 142 and 242 mayswitch between these conditions according to the format (4:2:0) andothers.

Furthermore, cbf_luma, cbf_cr, and cbf_cb indicate the presence orabsence of coefficients of luma or chroma. In other words, cbf_luma,cbf_cr, and cbf_cb are hierarchically lower than no residual_data_flagindicating the presence or absence of residual data. Here,no_residual_data_flag is used for the largest TU that can be selectedfor the size of a Cu in a relationship of Cu≧PU≧TU. More specifically,no_residual_data_flag is used in the top layer of a TU. On the otherhand, cbf_luma, cbf_cr, and cbf_cb are used in a layer lower than thelayer of no_residual_data_flag. The presence of no_residual_data_flagindicates that the subsequent blocks have no residual data. Furthermore,as the depth is greater, the residual data is probably present. Thus,the context control unit 142 and 242 can improve the coding efficiencyusing the hierarchical information for cbf_luma, cbf_cr, and cbf_cb. Inother words, the context control unit 142 and 242 may determine acontext according to a hierarchical depth of a data unit to which thecontrol parameter (cbf_luma, cbf_cr, and cbf_cb) of the current blockbelongs. On the other hand, since no_residual_data_flag is a flag thatdepends on a prediction mode, it is preferred that a fixed value thatdoes not depend on a depth as a context value is used.

Although the image coding apparatus and the image decoding apparatusaccording to Embodiments 1 to 3 of the present invention are described,the present invention is not limited to these Embodiments.

For example, at least part of the image coding apparatus, the imagedecoding apparatus, and functions of the modifications of theseapparatuses according to Embodiments 1 to 3 may be combined.

Furthermore, all the values and the logical values described above areexemplifications for specifically describing the present invention, andthe present invention is not limited by the exemplified values.

Furthermore, the divisions of the functional blocks in the blockdiagrams are examples. Thus, the functional blocks may be implemented asone functional block, one functional block may be divided into aplurality of functional blocks, and a part of the functions may beswitched to another functional block. Furthermore, a plurality offunctional blocks having similar functions may be processed by singlehardware or software in parallel or with time division.

The orders of the steps of the image coding method performed by theimage coding apparatus and the image decoding method performed by theimage decoding apparatus are for specifically describing the presentinvention, and may be an order other than the above orders. Furthermore,part of the steps may be performed simultaneously (in parallel) with theother steps.

Embodiment 4

The processing described in each of Embodiments can be simplyimplemented by a computer system by recording, onto a recording medium,a program for implementing the structure of the moving image codingmethod or the moving image decoding method described in Embodiment. Therecording medium may be any recording medium as long as the program canbe recorded thereon, such as a magnetic disk, an optical disc, amagnetic optical disc, an IC card, and a semiconductor memory.

Hereinafter, the applications to the moving image coding method or themoving image decoding method described in each of Embodiments and asystem using the same will be described.

FIG. 19 illustrates an overall configuration of a content providingsystem ex100 for implementing content distribution services. The areafor providing communication services is divided into cells of desiredsize, and base stations ex106 to ex110 which are fixed wireless stationsare placed in each of the cells.

The content providing system ex100 is connected to devices, such as acomputer ex111, a personal digital assistant (PDA) ex112, a cameraex113, a cellular phone ex114 and a game machine ex115, via an Internetex101, an Internet service provider ex102, a telephone network ex104, aswell as the base stations ex106 to ex110.

However, the configuration of the content providing system ex100 is notlimited to the configuration shown in FIG. 19, and a combination inwhich any of the elements are connected is acceptable. In addition, eachof the devices may be directly connected to the telephone network ex104,rather than via the base stations ex106 to ex110 which are the fixedwireless stations. Furthermore, the devices may be interconnected toeach other via a short distance wireless communication and others.

The camera ex113, such as a digital video camera, is capable ofcapturing moving images. A camera ex116, such as a digital video camera,is capable of capturing both still images and moving images.Furthermore, the cellular phone ex114 may be the one that meets any ofthe standards such as Global System for Mobile Communications (GSM),Code Division Multiple Access (CDMA), Wideband-Code Division MultipleAccess (W-CDMA), Long Term Evolution (LTE), and High Speed Packet Access(HSPA). Alternatively, the cellular phone ex114 may be a PersonalHandyphone System (PHS).

In the content providing system ex100, a streaming server ex103 isconnected to the camera ex113 and others via the telephone network ex104and the base station ex109, which enables distribution of a live showand others. For such a distribution, a content (for example, video of amusic live show) captured by the user using the camera ex113 is coded asdescribed above in each of Embodiments, and the coded content istransmitted to the streaming server ex103. On the other hand, thestreaming server ex103 carries out stream distribution of the receivedcontent data to the clients upon their requests. The clients include thecomputer ex111, the PDA ex112, the camera ex113, the cellular phoneex114, and the game machine ex115 that are capable of decoding theabove-mentioned coded data. Each of the devices that have received thedistributed data decodes and reproduces the coded data.

The captured data may be coded by the camera ex113 or the streamingserver ex103 that transmits the data, or the coding processes may beshared between the camera ex113 and the streaming server ex103.Similarly, the distributed data may be decoded by the clients or thestreaming server ex103, or the decoding processes may be shared betweenthe clients and the streaming server ex103. Furthermore, the data of thestill images and moving images captured by not only the camera ex113 butalso the camera ex116 may be transmitted to the streaming server ex103through the computer ex111. The coding processes may be performed by thecamera ex116, the computer ex111, or the streaming server ex103, orshared among them.

Furthermore, generally, the computer ex111 and an LSI ex500 included ineach of the devices perform such coding and decoding processes. The LSIex500 may be configured of a single chip or a plurality of chips.Software for coding and decoding moving images may be integrated intosome type of a recording medium (such as a CD-ROM, a flexible disk, ahard disk) that is readable by the computer ex111 and others, and thecoding and decoding processes may be performed using the software.Furthermore, when the cellular phone ex114 is equipped with a camera,the video data obtained by the camera may be transmitted. The video datais data coded by the LSI ex500 included in the cellular phone ex114.

Furthermore, the streaming server ex103 may be composed of servers andcomputers, and may decentralize data and process the decentralized data,record, or distribute data.

As described above, the clients can receive and reproduce the coded datain the content providing system ex100. In other words, the clients canreceive and decode information transmitted by the user, and reproducethe decoded data in real time in the content providing system ex100, sothat the user who does not have any particular right and equipment canimplement personal broadcasting.

The present invention is not limited to the above-mentioned contentproviding system ex100, and at least either the moving image codingapparatus or the moving image decoding apparatus described in each ofEmbodiments can be incorporated into a digital broadcasting system ex200as shown in FIG. 20. More specifically, a broadcast station ex201communicates or transmits, via radio waves to a broadcast satelliteex202, multiplexed data obtained by multiplexing the audio data and thevideo data. The video data is data coded according to the moving imagecoding method described in each of Embodiments. Upon receipt of thevideo data, the broadcast satellite ex202 transmits radio waves forbroadcasting. Then, a home-use antenna ex204 capable of receiving asatellite broadcast receives the radio waves. A device, such as atelevision (receiver) ex300 and a set top box (STB) ex217, decodes thereceived multiplexed data and reproduces the data.

Furthermore, a reader/recorder ex218 that (i) reads and decodes themultiplexed data recorded on a recording media ex215, such as a DVD anda BD, or (ii) codes video signals in the recording medium ex215, and insome cases, writes data obtained by multiplexing an audio signal on thecoded data can include the moving image decoding apparatus or the movingimage coding apparatus as shown in each of Embodiments. In this case,the reproduced video signals are displayed on the monitor ex219, andanother apparatus or system can reproduce the video signals, using therecording medium ex215 on which the multiplexed data is recorded.Furthermore, it is also possible to implement the moving image decodingapparatus in the set top box ex217 connected to the cable ex203 for acable television or the antenna ex204 for satellite and/or terrestrialbroadcasting, so as to display the video signals on the monitor ex219 ofthe television ex300. The moving image decoding apparatus may beincluded not in the set top box but in the television ex300.

FIG. 21 illustrates the television (receiver) ex300 that uses the movingimage coding method and the moving image decoding method described ineach of Embodiments. The television ex300 includes: a tuner ex301 thatobtains or provides multiplexed data obtained by multiplexing the audiodata and the video data through the antenna ex204 or the cable ex203,etc. that receives a broadcast; a modulation/demodulation unit ex302that demodulates the received multiplexed data or modulates data intomultiplexed data to be supplied outside; and amultiplexing/demultiplexing unit ex303 that demultiplexes the modulatedmultiplexed data into video data and audio data, or multiplexes thevideo data and audio data coded by the signal processing unit ex306 intodata.

Furthermore, the television ex300 further includes: a signal processingunit ex306 including an audio signal processing unit ex304 and a videosignal processing unit ex305 that decode audio data and video data andcode audio data and video data, respectively; a speaker ex307 thatprovides the decoded audio signal; and an output unit ex309 including adisplay unit ex308 that displays the decoded video signal, such as adisplay. Furthermore, the television ex300 includes an interface unitex317 including an operation input unit ex312 that receives an input ofa user operation. Furthermore, the television ex300 includes a controlunit ex310 that controls overall each constituent element of thetelevision ex300, and a power supply circuit unit ex311 that suppliespower to each of the elements. Other than the operation input unitex312, the interface unit ex317 may include: a bridge ex313 that isconnected to an external device, such as the reader/recorder ex218; aslot unit ex314 for enabling attachment of the recording medium ex216,such as an SD card; a driver ex315 to be connected to an externalrecording medium, such as a hard disk; and a modem ex316 to be connectedto a telephone network. Here, the recording medium ex216 canelectrically record information using a non-volatile/volatilesemiconductor memory element for storage. The constituent elements ofthe television ex300 are connected to one another through a synchronousbus.

First, a configuration in which the television ex300 decodes themultiplexed data obtained from outside through the antenna ex204 andothers and reproduces the decoded data will be described. In thetelevision ex300, upon receipt of a user operation from a remotecontroller ex220 and others, the multiplexing/demultiplexing unit ex303demultiplexes the multiplexed data demodulated by themodulation/demodulation unit ex302, under control of the control unitex310 including a CPU. Furthermore, the audio signal processing unitex304 decodes the demultiplexed audio data, and the video signalprocessing unit ex305 decodes the demultiplexed video data, using thedecoding method described in each of Embodiments, in the televisionex300. The output unit ex309 provides the decoded video signal and audiosignal outside. When the output unit ex309 provides the video signal andthe audio signal, the signals may be temporarily stored in buffers ex318and ex319, and others so that the signals are reproduced insynchronization with each other. Furthermore, the television ex300 mayread the multiplexed data not through a broadcast and others but fromthe recording media ex215 and ex216, such as a magnetic disk, an opticaldisc, and an SD card. Next, a configuration in which the televisionex300 codes an audio signal and a video signal, and transmits the dataoutside or writes the data on a recording medium will be described. Inthe television ex300, upon receipt of a user operation from the remotecontroller ex220 and others, the audio signal processing unit ex304codes an audio signal, and the video signal processing unit ex305 codesa video signal, under control of the control unit ex310 using the imagecoding method as described in each of Embodiments. Themultiplexing/demultiplexing unit ex303 multiplexes the coded videosignal and audio signal, and provides the resulting signal outside. Whenthe multiplexing/demultiplexing unit ex303 multiplexes the video signaland the audio signal, the signals may be temporarily stored in buffersex320 and ex321, and others so that the signals are reproduced insynchronization with each other. Here, the buffers ex318 to ex321 may beplural as illustrated, or at least one buffer may be shared in thetelevision ex300. Furthermore, data may be stored in a buffer other thanthe buffers ex318 to ex321 so that the system overflow and underflow maybe avoided between the modulation/demodulation unit ex302 and themultiplexing/demultiplexing unit ex303, for example.

Furthermore, the television ex300 may include a configuration forreceiving an AV input from a microphone or a camera other than theconfiguration for obtaining audio and video data from a broadcast or arecording medium, and may code the obtained data. Although thetelevision ex300 can code, multiplex, and provide outside data in thedescription, it may be not capable of performing all the processes butcapable of only one of receiving, decoding, and providing outside data.

Furthermore, when the reader/recorder ex218 reads or writes themultiplexed data from or in a recording medium, one of the televisionex300 and the reader/recorder ex218 may decode or code the multiplexeddata, and the television ex300 and the reader/recorder ex218 may sharethe decoding or coding.

As an example, FIG. 22 illustrates a configuration of an informationreproducing/recording unit ex400 when data is read or written from or inan optical disc. The information reproducing/recording unit ex400includes constituent elements ex401 to ex407 to be describedhereinafter. The optical head ex401 irradiates a laser spot on arecording surface of the recording medium ex215 that is an optical discto write information, and detects reflected light from the recordingsurface of the recording medium ex215 to read the information. Themodulation recording unit ex402 electrically drives a semiconductorlaser included in the optical head ex401, and modulates the laser lightaccording to recorded data. The reproduction demodulating unit ex403amplifies a reproduction signal obtained by electrically detecting thereflected light from the recording surface using a photo detectorincluded in the optical head ex401, and demodulates the reproductionsignal by separating a signal component recorded on the recording mediumex215 to reproduce the necessary information. The buffer ex404temporarily holds the information to be recorded on the recording mediumex215 and the information reproduced from the recording medium ex215. Adisk motor ex405 rotates the recording medium ex215. A servo controlunit ex406 moves the optical head ex401 to a predetermined informationtrack while controlling the rotation drive of the disk motor ex405 so asto follow the laser spot. The system control unit ex407 controls overallthe information reproducing/recording unit ex400. The reading andwriting processes can be implemented by the system control unit ex407using various information stored in the buffer ex404 and generating andadding new information as necessary, and by the modulation recordingunit ex402, the reproduction demodulating unit ex403, and the servocontrol unit ex406 that record and reproduce information through theoptical head ex401 while being operated in a coordinated manner. Thesystem control unit ex407 includes, for example, a microprocessor, andexecutes processing by causing a computer to execute a program for readand write.

Although the optical head ex401 irradiates a laser spot in thedescription, it may perform high-density recording using near fieldlight.

FIG. 23 schematically illustrates the recording medium ex215 that is theoptical disc. On the recording surface of the recording medium ex215,guide grooves are spirally formed, and an information track ex230records, in advance, address information indicating an absolute positionon the disk according to change in a shape of the guide grooves. Theaddress information includes information for determining positions ofrecording blocks ex231 that are a unit for recording data. An apparatusthat records and reproduces data reproduces the information track ex230and reads the address information so as to determine the positions ofthe recording blocks. Furthermore, the recording medium ex215 includes adata recording area ex233, an inner circumference area ex232, and anouter circumference area ex234. The data recording area ex233 is an areafor use in recording the user data. The inner circumference area ex232and the outer circumference area ex234 that are inside and outside ofthe data recording area ex233, respectively are for specific use exceptfor recording the user data. The information reproducing/recording unit400 reads and writes coded audio data, coded video data, or multiplexeddata obtained by multiplexing the coded audio data and the coded videodata, from and on the data recording area ex233 of the recording mediumex215.

Although an optical disc having a layer, such as a DVD and a BD isdescribed as an example in the description, the optical disc is notlimited to such, and may be an optical disc having a multilayerstructure and capable of being recorded on a part other than thesurface. Furthermore, the optical disc may have a structure formultidimensional recording/reproduction, such as recording ofinformation using light of colors with different wavelengths in the sameportion of the optical disc and recording information having differentlayers from various angles.

Furthermore, the car ex210 having the antenna ex205 can receive datafrom the satellite ex202 and others, and reproduce video on the displaydevice such as the car navigation system ex211 set in the car ex210, ina digital broadcasting system ex200. Here, a configuration of the carnavigation system ex211 will be the one for example, including a GPSreceiving unit in the configuration illustrated in FIG. 21. The samewill be true for the configuration of the computer ex111, the cellularphone ex114, and others.

FIG. 24A illustrates the cellular phone ex114 that uses the moving imagecoding method and the moving image decoding method described in each ofEmbodiments. The cellular phone ex114 includes: an antenna ex350 fortransmitting and receiving radio waves through the base station ex110; acamera unit ex365 capable of capturing moving and still images; and adisplay unit ex358 such as a liquid crystal display for displaying thedata such as decoded video captured by the camera unit ex365 or receivedby the antenna ex350. The cellular phone ex114 further includes: a mainbody unit including a set of operation keys ex366; an audio output unitex357 such as a speaker for output of audio; an audio input unit ex356such as a microphone for input of audio; a memory unit ex367 for storingcaptured video or still pictures, recorded audio, coded or decoded dataof the received video, the still images, e-mails, or others; and a slotunit ex364 that is an interface unit for a recording medium that storesdata in the same manner as the memory unit ex367.

Next, an example of a configuration of the cellular phone ex114 will bedescribed with reference to FIG. 24B. In the cellular phone ex114, amain control unit ex360 designed to control overall each unit of themain body including the display unit ex358 as well as the operation keysex366 is connected mutually, via a synchronous bus ex370, to a powersupply circuit unit ex361, an operation input control unit ex362, avideo signal processing unit ex355, a camera interface unit ex363, aliquid crystal display (LCD) control unit ex359, amodulation/demodulation unit ex352, a multiplexing/demultiplexing unitex353, an audio signal processing unit ex354, the slot unit ex364, andthe memory unit ex367.

When a call-end key or a power key is turned ON by a user's operation,the power supply circuit unit ex361 supplies the respective units withpower from a battery pack so as to activate the cell phone ex114.

In the cellular phone ex114, the audio signal processing unit ex354converts the audio signals collected by the audio input unit ex356 invoice conversation mode into digital audio signals under the control ofthe main control unit ex360 including a CPU, ROM, and RAM. Then, themodulation/demodulation unit ex352 performs spread spectrum processingon the digital audio signals, and the transmitting and receiving unitex351 performs digital-to-analog conversion and frequency conversion onthe data, so as to transmit the resulting data via the antenna ex350.Also, in the cellular phone ex114, the transmitting and receiving unitex351 amplifies the data received by the antenna ex350 in voiceconversation mode and performs frequency conversion and theanalog-to-digital conversion on the data.

Then, the modulation/demodulation unit ex352 performs inverse spreadspectrum processing on the data, and the audio signal processing unitex354 converts it into analog audio signals, so as to output them viathe audio output unit ex357. Furthermore, when an e-mail in datacommunication mode is transmitted, text data of the e-mail inputted byoperating the operation keys ex366 and others of the main body is sentout to the main control unit ex360 via the operation input control unitex362. The main control unit ex360 causes the modulation/demodulationunit ex352 to perform spread spectrum processing on the text data, andthe transmitting and receiving unit ex351 performs the digital-to-analogconversion and the frequency conversion on the resulting data totransmit the data to the base station ex110 via the antenna ex350. Whenan e-mail is received, processing that is approximately inverse to theprocessing for transmitting an e-mail is performed on the received data,and the resulting data is provided to the display unit ex358.

When video, still images, or video and audio in data communication modeis or are transmitted, the video signal processing unit ex355 compressesand codes video signals supplied from the camera unit ex365 using themoving image coding method shown in each of Embodiments, and transmitsthe coded video data to the multiplexing/demultiplexing unit ex353. Incontrast, during when the camera unit ex365 captures video, stillimages, and others, the audio signal processing unit ex354 codes audiosignals collected by the audio input unit ex356, and transmits the codedaudio data to the multiplexing/demultiplexing unit ex353.

The multiplexing/demultiplexing unit ex353 multiplexes the coded videodata supplied from the video signal processing unit ex355 and the codedaudio data supplied from the audio signal processing unit ex354, using apredetermined method. Then, the modulation/demodulation unit ex352performs spread spectrum processing on the multiplexed data, and thetransmitting and receiving unit ex351 performs digital-to-analogconversion and frequency conversion on the data so as to transmit theresulting data via the antenna ex350.

When receiving data of a video file which is linked to a Web page andothers in data communication mode or when receiving an e-mail with videoand/or audio attached, in order to decode the multiplexed data receivedvia the antenna ex350, the multiplexing/demultiplexing unit ex353demultiplexes the multiplexed data into a video data bit stream and anaudio data bitstream, and supplies the video signal processing unitex355 with the coded video data and the audio signal processing unitex354 with the coded audio data, through the synchronous bus ex370. Thevideo signal processing unit ex355 decodes the video signal using amoving image decoding method corresponding to the moving image codingmethod shown in each of Embodiments, and then the display unit ex358displays, for instance, the video and still images included in the videofile linked to the Web page via the LCD control unit ex359. Furthermore,the audio signal processing unit ex354 decodes the audio signal, and theaudio output unit ex357 provides the audio.

Furthermore, similarly to the television ex300, a terminal such as thecellular phone ex114 probably have 3 types of implementationconfigurations including not only (i) a transmitting and receivingterminal including both a coding apparatus and a decoding apparatus, butalso (ii) a transmitting terminal including only a coding apparatus and(iii) a receiving terminal including only a decoding apparatus. Althoughthe digital broadcasting system ex200 receives and transmits themultiplexed data obtained by multiplexing audio data onto video data inthe description, the multiplexed data may be data obtained bymultiplexing not audio data but character data related to video ontovideo data, and may be not multiplexed data but video data itself.

As such, the moving image coding method and the moving image decodingmethod in each of Embodiments can be used in any of the devices andsystems described. Thus, the advantages described in each of Embodimentscan be obtained.

Furthermore, the present invention is not limited to Embodiments, andvarious modifications and revisions are possible without departing fromthe scope of the present invention.

Embodiment 5

Video data can be generated by switching, as necessary, between (i) themoving image coding method or the moving image coding apparatus shown ineach of Embodiments and (ii) a moving image coding method or a movingimage coding apparatus in conformity with a different standard, such asMPEG-2, MPEG4-AVC, and VC-1.

Here, when a plurality of video data that conforms to the differentstandards is generated and is then decoded, the decoding methods need tobe selected to conform to the different standards. However, since towhich standard each of the plurality of the video data to be decodedconforms cannot be detected, there is a problem that an appropriatedecoding method cannot be selected.

In order to solve the problem, multiplexed data obtained by multiplexingaudio data and others onto video data has a structure includingidentification information indicating to which standard the video dataconforms. The specific structure of the multiplexed data including thevideo data generated in the moving image coding method and by the movingimage coding apparatus shown in each of Embodiments will be hereinafterdescribed. The multiplexed data is a digital stream in the MPEG-2Transport Stream format.

FIG. 25 illustrates a structure of multiplexed data. As illustrated inFIG. 25, the multiplexed data can be obtained by multiplexing at leastone of a video stream, an audio stream, a presentation graphics stream(PG), and an interactive graphics stream. The video stream representsprimary video and secondary video of a movie, the audio stream (IG)represents a primary audio part and a secondary audio part to be mixedwith the primary audio part, and the presentation graphics streamrepresents subtitles of a movie. Here, the primary video is normal videoto be displayed on a screen, and the secondary video is video to bedisplayed on a smaller window in the main video. Furthermore, theinteractive graphics stream represents an interactive screen to begenerated by arranging the GUI components on a screen. The video streamis coded in the moving image coding method or by the moving image codingapparatus shown in each of Embodiments, or in a moving image codingmethod or by a moving image coding apparatus in conformity with aconventional standard, such as MPEG-2, MPEG4-AVC, and VC-1. The audiostream is coded in accordance with a standard, such as Dolby-AC-3, DolbyDigital Plus, MLP, DTS, DTS-HD, and linear PCM.

Each stream included in the multiplexed data is identified by PID. Forexample, 0x1011 is allocated to the video stream to be used for video ofa movie, 0x1100 to 0x111F are allocated to the audio streams, 0x1200 to0x121F are allocated to the presentation graphics streams, 0x1400 to0x141F are allocated to the interactive graphics streams, 0x1B00 to0x1B1F are allocated to the video streams to be used for secondary videoof the movie, and 0x1A00 to 0x1A1F are allocated to the audio streams tobe used for the secondary video to be mixed with the primary audio.

FIG. 26 schematically illustrates how data is multiplexed. First, avideo stream ex235 composed of video frames and an audio stream ex238composed of audio frames are transformed into a stream of PES packetsex236 and a stream of PES packets ex239, and further into TS packetsex237 and TS packets ex240, respectively. Similarly, data of apresentation graphics stream ex241 and data of an interactive graphicsstream ex244 are transformed into a stream of PES packets ex242 and astream of PES packets ex245, and further into TS packets ex243 and TSpackets ex246, respectively. These TS packets are multiplexed into astream to obtain multiplexed data ex247.

FIG. 27 illustrates how a video stream is stored in a stream of PESpackets in more detail. The first bar in FIG. 27 shows a video framestream in a video stream. The second bar shows the stream of PESpackets. As indicated by arrows denoted as yy1, yy2, yy3, and yy4 inFIG. 27, the video stream is divided into pictures as I pictures, Bpictures, and P pictures each of which is a video presentation unit, andthe pictures are stored in a payload of each of the PES packets. Each ofthe PES packets has a PES header, and the PES header stores aPresentation Time-Stamp (PTS) indicating a display time of the picture,and a Decoding Time-Stamp (DTS) indicating a decoding time of thepicture.

FIG. 28 illustrates a format of TS packets to be finally written on themultiplexed data. Each of the TS packets is a 188-byte fixed lengthpacket including a 4-byte TS header having information, such as a PIDfor identifying a stream and a 184-byte TS payload for storing data. ThePES packets are divided, and stored in the TS payloads, respectively.When a BD ROM is used, each of the TS packets is given a 4-byteTP_Extra_Header, thus resulting in 192-byte source packets. The sourcepackets are written on the multiplexed data. The TP_Extra_Header storesinformation such as an Arrival_Time_Stamp (ATS). The ATS shows atransfer start time at which each of the TS packets is to be transferredto a PID filter. The numbers incrementing from the head of themultiplexed data are called source packet numbers (SPNs) as shown at thebottom of FIG. 28.

Each of the TS packets included in the multiplexed data includes notonly streams of audio, video, subtitles and others, but also a ProgramAssociation Table (PAT), a Program Map Table (PMT), and a Program ClockReference (PCR). The PAT shows what a PID in a PMT used in themultiplexed data indicates, and a PID of the PAT itself is registered aszero. The PMT stores PIDs of the streams of video, audio, subtitles andothers included in the multiplexed data, and attribute information ofthe streams corresponding to the PIDs. The PMT also has variousdescriptors relating to the multiplexed data. The descriptors haveinformation such as copy control information showing whether copying ofthe multiplexed data is permitted or not. The PCR stores STC timeinformation corresponding to an ATS showing when the PCR packet istransferred to a decoder, in order to achieve synchronization between anArrival Time Clock (ATC) that is a time axis of ATSs, and an System TimeClock (STC) that is a time axis of PTSs and DTSs.

FIG. 29 illustrates the data structure of the PMT in detail. A PMTheader is disposed at the top of the PMT. The PMT header describes thelength of data included in the PMT and others. A plurality ofdescriptors relating to the multiplexed data is disposed after the PMTheader. Information such as the copy control information is described inthe descriptors. After the descriptors, a plurality of pieces of streaminformation relating to the streams included in the multiplexed data isdisposed. Each piece of stream information includes stream descriptorseach describing information, such as a stream type for identifying acompression codec of a stream, a stream PID, and stream attributeinformation (such as a frame rate or an aspect ratio). The streamdescriptors are equal in number to the number of streams in themultiplexed data.

When the multiplexed data is recorded on a recording medium and others,it is recorded together with multiplexed data information files.

Each of the multiplexed data information files is management informationof the multiplexed data as shown in FIG. 30. The multiplexed datainformation files are in one to one correspondence with the multiplexeddata, and each of the files includes multiplexed data information,stream attribute information, and an entry map.

As illustrated in FIG. 30, the multiplexed data information includes asystem rate, a reproduction start time, and a reproduction end time. Thesystem rate indicates the maximum transfer rate at which a system targetdecoder to be described later transfers the multiplexed data to a PIDfilter. The intervals of the ATSs included in the multiplexed data areset to not higher than a system rate. The reproduction start timeindicates a PTS in a video frame at the head of the multiplexed data. Aninterval of one frame is added to a PTS in a video frame at the end ofthe multiplexed data, and the PTS is set to the reproduction end time.

As shown in FIG. 31, a piece of attribute information is registered inthe stream attribute information, for each PID of each stream includedin the multiplexed data. Each piece of attribute information hasdifferent information depending on whether the corresponding stream is avideo stream, an audio stream, a presentation graphics stream, or aninteractive graphics stream. Each piece of video stream attributeinformation carries information including what kind of compression codecis used for compressing the video stream, and the resolution, aspectratio and frame rate of the pieces of picture data that is included inthe video stream. Each piece of audio stream attribute informationcarries information including what kind of compression codec is used forcompressing the audio stream, how many channels are included in theaudio stream, which language the audio stream supports, and how high thesampling frequency is. The video stream attribute information and theaudio stream attribute information are used for initialization of adecoder before the player plays back the information.

In Embodiment 5, the multiplexed data to be used is of a stream typeincluded in the PMT. Furthermore, when the multiplexed data is recordedon a recording medium, the video stream attribute information includedin the multiplexed data information is used. More specifically, themoving image coding method or the moving image coding apparatusdescribed in each of Embodiments includes a step or a unit forallocating unique information indicating video data generated by themoving image coding method or the moving image coding apparatus in eachof Embodiments, to the stream type included in the PMT or the videostream attribute information. With the structure, the video datagenerated by the moving image coding method or the moving image codingapparatus described in each of Embodiments can be distinguished fromvideo data that conforms to another standard.

Furthermore, FIG. 32 illustrates steps of the moving image decodingmethod according to Embodiment 5. In Step exS100, the stream typeincluded in the PMT or the video stream attribute information isobtained from the multiplexed data. Next, in Step exS101, it isdetermined whether or not the stream type or the video stream attributeinformation indicates that the multiplexed data is generated by themoving image coding method or the moving image coding apparatus in eachof Embodiments. When it is determined that the stream type or the videostream attribute information indicates that the multiplexed data isgenerated by the moving image coding method or the moving image codingapparatus in each of Embodiments, in Step exS102, the stream type or thevideo stream attribute information is decoded by the moving imagedecoding method in each of Embodiments. Furthermore, when the streamtype or the video stream attribute information indicates conformance tothe conventional standards, such as MPEG-2, MPEG4-AVC, and VC-1, in StepexS103, the stream type or the video stream attribute information isdecoded by a moving image decoding method in conformity with theconventional standards.

As such, allocating a new unique value to the stream type or the videostream attribute information enables determination whether or not themoving image decoding method or the moving image decoding apparatus thatis described in each of Embodiments can perform decoding. Even upon aninput of multiplexed data that conforms to a different standard, anappropriate decoding method or apparatus can be selected. Thus, itbecomes possible to decode information without any error. Furthermore,the moving image coding method or apparatus, or the moving imagedecoding method or apparatus in Embodiment 5 can be used in the devicesand systems described above.

Embodiment 6

Each of the moving image coding method, the moving image codingapparatus, the moving image decoding method, and the moving imagedecoding apparatus in each of Embodiments is typically achieved in theform of an integrated circuit or a Large Scale Integrated (LSI) circuit.As an example of the LSI, FIG. 33 illustrates a configuration of the LSIex500 that is made into one chip. The LSI ex500 includes elements ex501,ex502, ex503, ex504, ex505, ex506, ex507, ex508, and ex509 to bedescribed below, and the elements are connected to each other through abus ex510. The power supply circuit unit ex505 is activated by supplyingeach of the elements with power when the power supply circuit unit ex505is turned on.

For example, when coding is performed, the LSI ex500 receives an AVsignal from a microphone ex117, a camera ex113, and others through an AV10 ex509 under control of a control unit ex501 including a CPU ex502, amemory controller ex503, a stream controller ex504, and a drivingfrequency control unit ex512. The received AV signal is temporarilystored in an external memory ex511, such as an SDRAM. Under control ofthe control unit ex501, the stored data is segmented into data portionsaccording to the processing amount and speed to be transmitted to asignal processing unit ex507. Then, the signal processing unit ex507codes an audio signal and/or a video signal. Here, the coding of thevideo signal is the coding described in each of Embodiments.Furthermore, the signal processing unit ex507 sometimes multiplexes thecoded audio data and the coded video data, and a stream IO ex506provides the multiplexed data outside. The provided multiplexed data istransmitted to the base station ex107, or written on the recording mediaex215. When data sets are multiplexed, the data sets should betemporarily stored in the buffer ex508 so that the data sets aresynchronized with each other.

Although the memory ex511 is an element outside the LSI ex500, it may beincluded in the LSI ex500. The buffer ex508 is not limited to onebuffer, but may be composed of buffers. Furthermore, the LSI ex500 maybe made into one chip or a plurality of chips.

Furthermore, although the control unit ex501 includes the CPU ex502, thememory controller ex503, the stream controller ex504, the drivingfrequency control unit ex512, the configuration of the control unitex501 is not limited to such. For example, the signal processing unitex507 may further include a CPU. Inclusion of another CPU in the signalprocessing unit ex507 can improve the processing speed. Furthermore, asanother example, the CPU ex502 may serve as or be a part of the signalprocessing unit ex507, and, for example, may include an audio signalprocessing unit. In such a case, the control unit ex501 includes thesignal processing unit ex507 or the CPU ex502 including a part of thesignal processing unit ex507.

The name used here is LSI, but it may also be called IC, system LSI,super LSI, or ultra LSI depending on the degree of integration.

Moreover, ways to achieve integration are not limited to the LSI, and aspecial circuit or a general purpose processor and so forth can alsoachieve the integration. Field Programmable Gate Array (FPGA) that canbe programmed after manufacturing LSIs or a reconfigurable processorthat allows re-configuration of the connection or configuration of anLSI can be used for the same purpose.

In the future, with advancement in semiconductor technology, a brand-newtechnology may replace LSI. The functional blocks can be integratedusing such a technology. The possibility is that the present inventionis applied to biotechnology.

Embodiment 7

When video data is decoded by the moving image coding method or by themoving image coding apparatus described in each of Embodiments, comparedto when video data that conforms to a conventional standard, such asMPEG-2, MPEG4-AVC, and VC-1, the computing amount probably increases.Thus, the LSI ex500 needs to be set to a driving frequency higher thanthat of the CPU ex502 to be used when video data in conformity with theconventional standard is decoded. However, when the driving frequency isset higher, there is a problem that the power consumption increases.

In order to solve the problem, the moving image decoding apparatus, suchas the television ex300 and the LSI ex500 is configured to determine towhich standard the video data conforms, and switch between the drivingfrequencies according to the determined standard. FIG. 34 illustrates aconfiguration ex800 in Embodiment 7. A driving frequency switching unitex803 sets a driving frequency to a higher driving frequency when videodata is generated by the moving image coding method or the moving imagecoding apparatus described in each of Embodiments. Then, the drivingfrequency switching unit ex803 instructs a decoding processing unitex801 that executes the moving image decoding method described in eachof Embodiments to decode the video data. When the video data conforms tothe conventional standard, the driving frequency switching unit ex803sets a driving frequency to a lower driving frequency than that of thevideo data generated by the moving image coding method or the movingimage coding apparatus described in each of Embodiments. Then, thedriving frequency switching unit ex803 instructs the decoding processingunit ex802 that conforms to the conventional standard to decode thevideo data.

More specifically, the driving frequency switching unit ex803 includesthe CPU ex502 and the driving frequency control unit ex512 in FIG. 33.Here, each of the decoding processing unit ex801 that executes themoving image decoding method described in each of Embodiments and thedecoding processing unit ex802 that conforms to the conventionalstandard corresponds to the signal processing unit ex507 in FIG. 33. TheCPU ex502 determines to which standard the video data conforms. Then,the driving frequency control unit ex512 determines a driving frequencybased on a signal from the CPU ex502. Furthermore, the signal processingunit ex507 decodes the video data based on a signal from the CPU ex502.For example, the identification information described in Embodiment 5 isprobably used for identifying the video data. The identificationinformation is not limited to the one described in Embodiment 5 but maybe any information as long as the information indicates to whichstandard the video data conforms. For example, when which standard videodata conforms to can be determined based on an external signal fordetermining that the video data is used for a television or a disk,etc., the determination may be made based on such an external signal.Furthermore, the CPU ex502 selects a driving frequency based on, forexample, a look-up table in which the standards of the video data areassociated with the driving frequencies as shown in FIG. 36. The drivingfrequency can be selected by storing the look-up table in the bufferex508 and an internal memory of an LSI and with reference to the look-uptable by the CPU ex502.

FIG. 35 illustrates steps for executing a method in Embodiment 7. First,in Step exS200, the signal processing unit ex507 obtains identificationinformation from the multiplexed data. Next, in Step exS201, the CPUex502 determines whether or not the video data is generated based on theidentification information by the coding method and the coding apparatusdescribed in each of Embodiments. When the video data is generated bythe coding method and the coding apparatus described in each ofEmbodiments, in Step exS202, the CPU ex502 transmits a signal forsetting the driving frequency to a higher driving frequency to thedriving frequency control unit ex512. Then, the driving frequencycontrol unit ex512 sets the driving frequency to the higher drivingfrequency. On the other hand, when the identification informationindicates that the video data conforms to the conventional standard,such as MPEG-2, MPEG4-AVC, and VC-1, in Step exS203, the CPU ex502transmits a signal for setting the driving frequency to a lower drivingfrequency to the driving frequency control unit ex512. Then, the drivingfrequency control unit ex512 sets the driving frequency to the lowerdriving frequency than that in the case where the video data isgenerated by the coding method and the coding apparatus described ineach of Embodiments.

Furthermore, along with the switching of the driving frequencies, thepower conservation effect can be improved by changing the voltage to beapplied to the LSI ex500 or an apparatus including the LSI ex500. Forexample, when the driving frequency is set lower, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set to a voltage lower than that in the case where the drivingfrequency is set higher.

Furthermore, when the computing amount for decoding is larger, thedriving frequency may be set higher, and when the computing amount fordecoding is smaller, the driving frequency may be set lower as themethod for setting the driving frequency. Thus, the setting method isnot limited to the ones described above. For example, when the computingamount for decoding video data in conformity with MPEG4-AVC is largerthan the computing amount for decoding video data generated by themoving image coding method and the moving image coding apparatusdescribed in each of Embodiments, the driving frequency is probably setin reverse order to the setting described above.

Furthermore, the method for setting the driving frequency is not limitedto the method for setting the driving frequency lower. For example, whenthe identification information indicates that the video data isgenerated by the moving image coding method and the moving image codingapparatus described in each of Embodiments, the voltage to be applied tothe LSI ex500 or the apparatus including the LSI ex500 is probably sethigher. When the identification information indicates that the videodata conforms to the conventional standard, such as MPEG-2, MPEG4-AVC,and VC-1, the voltage to be applied to the LSI ex500 or the apparatusincluding the LSI ex500 is probably set lower. As another example, whenthe identification information indicates that the video data isgenerated by the moving image coding method and the moving image codingapparatus described in each of Embodiments, the driving of the CPU ex502does not probably have to be suspended. When the identificationinformation indicates that the video data conforms to the conventionalstandard, such as MPEG-2, MPEG4-AVC, and VC-1, the driving of the CPUex502 is probably suspended at a given time because the CPU ex502 hasextra processing capacity. Even when the identification informationindicates that the video data is generated by the moving image codingmethod and the moving image coding apparatus described in each ofEmbodiments, in the case where the CPU ex502 may have a time delay, thedriving of the CPU ex502 is probably suspended at a given time. In sucha case, the suspending time is probably set shorter than that in thecase where when the identification information indicates that the videodata conforms to the conventional standard, such as MPEG-2, MPEG4-AVC,and VC-1.

Accordingly, the power conservation effect can be improved by switchingbetween the driving frequencies in accordance with the standard to whichthe video data conforms. Furthermore, when the LSI ex500 or theapparatus including the LSI ex500 is driven using a battery, the batterylife can be extended with the power conservation effect.

Embodiment 8

There are cases where a plurality of video data that conforms todifferent standards, is provided to the devices and systems, such as atelevision and a cellular phone. In order to enable decoding theplurality of video data that conforms to the different standards, thesignal processing unit ex507 of the LSI ex500 needs to conform to thedifferent standards. However, the problems of increase in the scale ofthe circuit of the LSI ex500 and increase in the cost arise with theindividual use of the signal processing units ex507 that conform to therespective standards.

In order to solve the problem, what is conceived is a configuration inwhich the decoding processing unit for implementing the moving imagedecoding method described in each of Embodiments and the decodingprocessing unit that conforms to the conventional standard, such asMPEG-2, MPEG4-AVC, and VC-1 are partly shared. Ex900 in FIG. 37A showsan example of the configuration. For example, the moving image decodingmethod described in each of Embodiments and the moving image decodingmethod that conforms to MPEG4-AVC have, partly in common, the details ofprocessing, such as entropy coding, inverse quantization, deblockingfiltering, and motion compensated prediction. The details of processingto be shared probably include use of a decoding processing unit ex902that conforms to MPEG4-AVC. In contrast, a dedicated decoding processingunit ex901 is probably used for other processing unique to the presentinvention. Since the present invention is characterized by thearithmetic decoding in particular, for example, the dedicated decodingprocessing unit ex901 is used for the arithmetic decoding. Otherwise,the decoding processing unit is probably shared for one of the inversequantization, deblocking filtering, and motion compensation, or all ofthe processing. The decoding processing unit for implementing the movingimage decoding method described in each of Embodiments may be shared forthe processing to be shared, and a dedicated decoding processing unitmay be used for processing unique to that of MPEG4-AVC.

Furthermore, ex1000 in FIG. 37B shows another example in whichprocessing is partly shared. This example uses a configuration includinga dedicated decoding processing unit ex1001 that supports the processingunique to the present invention, a dedicated decoding processing unitex1002 that supports the processing unique to another conventionalstandard, and a decoding processing unit ex1003 that supports processingto be shared between the moving image decoding method in the presentinvention and the conventional moving image decoding method. Here, thededicated decoding processing units ex1001 and ex1002 are notnecessarily specialized for the processing of the present invention andthe processing of the conventional standard, and may be the ones capableof implementing general processing. Furthermore, the configuration ofEmbodiment 8 can be implemented by the LSI ex500.

As such, reducing the scale of the circuit of an LSI and reducing thecost are possible by sharing the decoding processing unit for theprocessing to be shared between the moving image decoding method in thepresent invention and the moving image decoding method in conformitywith the conventional standard.

Although only some exemplary embodiments of the present invention havebeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of the present invention. Accordingly, all such modificationsare intended to be included within the scope of the present invention.

INDUSTRIAL APPLICABILITY

The present invention is applicable to an image coding method, an imagedecoding method, an image coding apparatus, and an image decodingapparatus, and in particular, is applicable to an image coding method,an image decoding method, an image coding apparatus, and an imagedecoding apparatus which use arithmetic coding and arithmetic decoding.

1. An image decoding method using arithmetic decoding, the methodcomprising: determining a context for use in a current block to beprocessed, from among a plurality of contexts; performing arithmeticdecoding on a bit sequence corresponding to the current block, using thedetermined context to reconstruct a binary sequence, the bit sequencebeing obtained by performing arithmetic coding on a control parameter ofthe current block; and inversely binarizing the binary sequence toreconstruct the control parameter of the current block, wherein thedetermining of a context includes: determining a signal type of thecontrol parameter of the current block; determining the context under afirst condition that decoded control parameters of neighboring blocks ofthe current block are used, when the signal type is a first type, theneighboring blocks being a left block and an upper block of the currentblock; and determining the context under a second condition that thedecoded control parameter of the upper block is not used, when thesignal type is a second type different from the first type, the firsttype is one of “split_coding_unit_flag” and “skip_flag”, and the secondtype is one of “cbf_luma”, “cbf_cb”, and “cbf_cr”.
 2. The image decodingmethod according to claim 1, wherein the second condition is a conditionthat the decoded control parameters of the left block and the upperblock are not used.
 3. The image decoding method according to claim 2,wherein in the determining of a context, a predetermined context isdetermined under the second condition, as the context for use in thearithmetic decoding of the current block, when the signal type is thesecond type.
 4. The image decoding method according to claim 2, whereinthe context is determined under the second condition according to ahierarchical depth of a data unit to which the control parameter of thecurrent block belongs, when the signal type is the second type.
 5. Theimage decoding method according to claim 1, wherein the determining of acontext further includes: determining whether or not the decoded controlparameter of the upper block is available in decoding, based on aposition of the current block; and determining the context under thesecond condition, when the decoded control parameter of the upper blockis not available.
 6. The image decoding method according to claim 5,wherein in the determining of a context, it is determined that thedecoded control parameter of the upper block is not available indecoding, when the current block is at a slice boundary.
 7. The imagedecoding method according to claim 5, wherein in the determining of acontext, it is determined whether or not the decoded control parameterof the upper block is available in decoding, according to a hierarchicaldepth of a data unit to which the control parameter of the current blockbelongs.
 8. The image decoding method according to claim 1, wherein thesecond type is a control parameter having a predetermined datastructure.
 9. The image decoding method according to claim 1, whereinthe determining of a context further includes determining a context of acontrol parameter of a second unit smaller than a first unit byswitching between the first condition and the second condition, based ona control parameter of the first unit.
 10. The image decoding methodaccording to claim 1, wherein the determining of a context furtherincludes determining a context using a different condition for each casewhere the signal type is the “cbf_luma”, or the signal type is one ofthe “cbfcb” and the “cbf cr”.
 11. The image decoding method according toclaim 1, wherein the “split_coding_unit_flag” indicates whether or notthe current block is partitioned into a plurality of blocks, the“skip_flag” indicates whether or not the current block is to be skipped,the “cbf_luma” indicates whether or not a luma transform block of thecurrent block contains one or more transform coefficient levels notequal to 0, the “cbf_cb” indicates whether or not a Cb transform blockof the current block contains one or more transform coefficient levelsnot equal to 0, and the “cbf_cr” indicates whether or not a Cr transformblock of the current block contains one or more transform coefficientlevels not equal to
 0. 12. The image decoding method according to claim1, wherein decoding processes in accordance with a first standard anddecoding processes in accordance with a second standard are switchedaccording to an identifier indicating one of the first standard and thesecond standard, the identifier being included in a coded signal, andthe determining of a context, the performing, and the inverselybinarizing are performed as the decoding processes in accordance withthe first standard, when the identifier indicates the first standard.13. An image coding method using arithmetic coding, the methodcomprising: binarizing a control parameter of a current block to beprocessed to generate a binary sequence; determining a context for usein the current block, from among a plurality of contexts; and performingarithmetic coding on the binary sequence using the determined context togenerate a bit sequence, wherein the determining of a context includes:determining a signal type of the control parameter of the current block;determining the context under a first condition that control parametersof neighboring blocks of the current block are used, when the signaltype is a first type, the neighboring blocks being a left block and anupper block of the current block; and determining the context under asecond condition that the control parameter of the upper block is notused, when the signal type is a second type different from the firsttype, the first type is one of “split_coding_unit_flag” and “skip_flag”,and the second type is one of “cbf luma”, “cbf_cb”, and “cbf_cr”.
 14. Animage decoding apparatus using arithmetic decoding, the apparatuscomprising: a context control unit configured to determine a context foruse in a current block to be processed, from among a plurality ofcontexts; an arithmetic decoding unit configured to perform arithmeticdecoding on a bit sequence corresponding to the current block, using thedetermined context to reconstruct a binary sequence, the bit sequencebeing obtained by performing arithmetic coding on a control parameter ofthe current block; and an inverse binarization unit configured toinversely binarize the binary sequence to reconstruct the controlparameter of the current block, wherein the context control unit isconfigured to: determine a signal type of the control parameter of thecurrent block; determine the context under a first condition thatdecoded control parameters of neighboring blocks of the current blockare used, when the signal type is a first type, the neighboring blocksbeing a left block and an upper block of the current block; anddetermine the context under a second condition that the decoded controlparameter of the upper block is not used, when the signal type is asecond type different from the first type, the first type is one of“split_coding_unit_flag” and “skip_flag”, and the second type is one of“cbf_luma”, “cbf_cb”, and “cbf_cr”.
 15. An image coding apparatus usingarithmetic coding, the apparatus comprising: a binarization unitconfigured to binarize a control parameter of a current block to beprocessed to generate a binary sequence; a context control unitconfigured to determine a context for use in the current block, fromamong a plurality of contexts; and an arithmetic coding unit configuredto perform arithmetic coding on the binary sequence using the determinedcontext to generate a bit sequence, wherein the context control unit isconfigured to: determine a signal type of the control parameter of thecurrent block; determine the context under a first condition thatcontrol parameters of neighboring blocks of the current block are used,when the signal type is a first type, the neighboring blocks being aleft block and an upper block of the current block; and determine thecontext under a second condition that the control parameter of the upperblock is not used, when the signal type is a second type different fromthe first type, the first type is one of “split_coding_unit_flag” and“skip_flag”, and the second type is one of “cbf_luma”, “cbf_cb”, and“cbf_cr”.
 16. An image coding and decoding apparatus comprising: theimage decoding apparatus according to claim 14; and the image codingapparatus according to claim 15.